No argument with that here, but I've always thought the RN's share of the purchase was small anyway, but we don't really know how this will affect the force structure at all yet, one report suggests that the RAF Merlins will be 'marinised', maybe the RN get these to replace their Seakings, but then what happens to the Pumas?
With money being tight, the Chinook represents the best compromise 'bang for buck' option, particularly if Osprey is ruled out. Range, load carrying capacity and speed is outstanding. It already forms the backbone of the SF rotary flight and is deemed absolutely essential for long-range missions requiring the insertion of troops, kit and wheeled vehicles. The UK has already zero-houred older versions to extend their life-span, the knowledge and infrastructure is already in place to absorb more units so to me it would make complete sense. Plus cost savings will be made by reducing the need to absorb a brand-new airframe training programme.
The AW149 has been pushed before as a cheap solution, though smaller than the Merlin and larger than the Wildcat (AW159), it does not offer a capability jump or fill a much needed requirement gap, it certainly doesn't compare with what an extra couple of Chinook sqn's brings to the table. Wildcat will also take up the liaison / armed-recce role currently enjoyed by army Lynx/Gazelle's to compliment the Apache, thus negating the need for a AW149 sized airframe or more AW159's.
Puma currently forms the backbone of the RAF'S battlefield taxis. I'm sure battlegroup commanders would much prefer to have the added capability of Chinook on call, after all Pumas can't lift vehicles, 105mm's + ammo, sustain a full trauma medical team and still have room for casualties.
The current Chinook crew of three operates a machine, which carries so much more than a medium lift helo, so adding capacity without increasing crew numbers with all associated knock-on financial implications makes sense. Merlin can provide the much needed support for RM operations, it has a much greater capacity than the SeaKing, Blackhawk (being forced to crouch down is right royal pain) or NH90 and comes with a very useful rear-ramp.
The new QE class lifts will be large enough to take the Chinook (QE could host 25 according to press reports?), and I'm sure any Ocean replacement will do the same. I'm also convinced the UK will be smart enough to specify folding rotors as they did with Apache (the only nation operating the machine to do so thus far).