Cuts to the Royal Marines
The 7200 Royal Marines will be cut by 650 (earlier 500 had been an indication), but not from the 3rd Commando Brigade total. The Fleet Protection Group will lose posts, but all its squadrons and units should be safe.
Leuchars and Lossiemouth
Operating Typhoon from RAF Lossiemouth for 25 years, including transfer cost as the fleet and associated personnel moves in from Leuchars will cost 604 million pounds. Operating the same fleet from Leuchars would have cost 565 millions on the same period. Having decided that the Typhoon force North will go at Lossiemouth, preparation of the infrastructure at Lossiemouth is to start "right away" to be ready to receive the Typhoon force as the last two squadrons are stood up directly in Lossie. However, the build-up will take place over time and Leuchars will remain a working RAF base until 2014, meaning that probably 6 Squadron RAF will move into Lossie only later on, and for the next few years it'll continue to deliver QRA service from its current position.
Joint Combat Aircraft
The F35 so far cost the UK 1,825 million, all coming from the Defence Budget. UK companies have already won JSF production contracts worth 15% by value of the work on each aircraft and are therefore well placed to win future maintenance and support work as well. Recently, the estimate value of such 15% share was put at 35 billion pounds.
Meanwhile, activity related to the F35 is to increase as the UK works towards placing its first orders.
The UK's exact requirement post-SDSR for the F-35 has yet to be set, but the Ministry of Defence has previously identified a need for up to 138 of the aircraft. An initial three F-35Bs were ordered to participate alongside the US military during initial operational test and evaluation of the new aircraft, but the allies are working out the details of a deal to exchange the last example for an F-35C following the UK's switch of variant.
The new type is expected to achieve Initial Operating Capability as a land-based asset from roughly 2018, before launching embarked operations around 2020. In the NAO Major Projects report 2010 (the most recent review of MOD programmes available at the moment, even if SDSR is likely to have changed more than a thing) indicates the Initial Operating Capability of F35 as "6 fighter jets at Readiness Level 2 (2 to 5 days notice) for embarkation for operations on the aircraft carrier" and the Full Operating Capability as "36 Force Elements at readiness", in other words 3 frontline, carrier-capable squadrons, implying that more planes (and at least another squadron) would sustain this. For example, the Tornado GR4 fleet, following SDSR, is going down, by 2015, from 40 Force Elements at readiness to 18, but retaining a total fleet of 96 planes in five squadrons plus OCU at least until around 2017, more likely 2018 - 2020 as F35 introduction must be balanced with the planned draw-down of the Tornado GR4 force: an activity that Liam Fox says will be "particularly challenging".
Some level of funding commitment will be required next year, to cover the order of long-lead items for an initial batch of 16 aircraft to be built during the programme's low-rate initial production phase (ending in 2016 after the latest programme restructuring). In particular, the 16 planes, according to the most recent Memorandum of Understanding (scroll down to page 88) signed by JSF partners, would be 7 ordered in 2013 and 9 in 2015, with expected delivery in 2015 and 2017 (from order to delivery, Lockheed Martin indicates two years as the time necessary). According to the MOU, 11 more orders (these would be, according to current plan, Full-Rate Production airplanes) would follow in 2016, 3 in 2017, 6 in 2018, 14 in 2019, 10 in 2020, 2 in 2021, 4 in 2022, 14 in 2023 for a total of 80. By 2020, consider the two years delivery time, the UK could have 36 planes plus 3 test airframes, compatible with the "40 F35 in 2020" figure which stubbornly circulated post SDSR.
80 airframes should be enough for 4 Squadrons and OCU.
The MOU displays further orders, up to 2027, to reach a total of 138 UK planes, but the MOD Business Plans 2010 and 2011 both showed an "end of activity" for F35 programme in 2023, which might mean end of the procurement effort after orders for a maximum of 80 airframes.
Post SDSR, RAF officers continued to declare that the long term target still is for "around 100".
UK Military Flight Training System
This December, ASCENT Flight Training, the industrial joint venture which delivers to the UK the military training for pilots of fixed and rotary wing of all three services, will issue the detailed request for proposals to continue the aircraft service provision competition, as part of the UK Military Flying Training System programme. Programme value is not disclosed, and locations of future training have not been confirmed. Several training planes in the fleet are expected to be replaced, including the Tucano and Tutor, while a replacement for the retired Dominie is also sought. Details are provided on this site, at the UKMFTS page.
Analysis to date has indicated that Unmanned Combat Air Systems (UCAS), in combination with manned systems, could form part of a cost effective solution for future air-to-air and air-to-ground combat roles. Ongoing research is focused on developing concepts and assessing their performance with a view to shaping a future UCAS programme. Such work includes the Taranis technology demonstrator, which the Ministry of Defence is developing in partnership with a BAE Systems-led industry team and which should soon enough fly for the first time at Woomera range, Australia.
Cooperation with France, according to the recent bilateral agreements, will involve UCAS activity, with a notional 2030 In-Service Date target.
Unfortunately, the written answer do not provide any additional information: in particular, it would be interesting to recognize what impact a 2009 Royal Navy study on the use of UCAS on the CVF carriers has eventually had on wider UCAS planning.
Entry in Service of Astutes and Type 45s
HMS Astute, commissioned April 2010, Operational service start in late 2012
HMS Ambush 2013
HMS Artful 2015
HMS Audacious 2018
HMS Agamemnon 2020
HMS Anson 2022
HMS Ajax 2024
HMS Dragon 2012
HMS Defender 2013
HMS Duncan 2014
Next year HMS Daring, Dauntless and Diamond should all experience their first deployment. For HMS Daring, planning assumed its deployment as escort for HMS Illustrious, itself planned to replace HMS Ocean in Libya ops. The recent developments in Libya might change the plans by removing the need for this deployment.
HMS Ocean replacement, future LPH capability
Debates during the buildup of the Parliamentary Defence Committee report on the SDSR had seen declarations about HMS Ocean leaving active service in 2016, probably to be replaced by HMS Queen Elizabeth.
The recent answer by Peter Luff reopens the scenario:
The means for delivering our landing platform helicopter capability after 2020 have not yet been decided, nor has the eventual out-of-service date of HMS Ocean, which provides the current capability. These decisions will be influenced by the evolving plan for the introduction into service of the new Queen Elizabeth class aircraft carriers.Can we hope for a dedicate LHD as replacement? Probably no. But one can dream...
155 mm naval guns: hopes still exist?
Dr Julian Lewis: To ask the Secretary of State for Defence what his policy is on the replacement of existing warship guns by ones of 155mm; and if he will make a statement on his policy, with special reference to (a) the future frigate fleet and (b) Type 45 destroyers. 
Peter Luff: No decision on the calibre of the new Maritime Indirect Fire System (the new naval gun) has yet been made. This will be taken when work to consider the available options under the Future Maritime Fires Concept Phase is complete in around mid-2012.
The MOD cut funding to the 155 TMF BAe development programme in 2010. I'm not aware if BAE has been continuing with its own funding, but i've expressed my hope many times that they would self-finance development.
If a 155 mm "Army-compatible" solution still exists, it has my support.
Otherwise, the likely options are the retention of the immortal 114 mm gun, or the adoption of 127 mm, almost certainly via Oto Melara/Babcock joint venture, marketing the Oto Melara 127/64 Lightweight gun mount.