Well, I have been following this thread for a few weeks now, and I need to say that most of you are seriously wrong.
It's not less Chinooks to deliver the effect, it's fewer.
Now I've got that out of my system:
I honestly believe Merlin Mk 4 for CHF will be the best solution for defence, and Merlin Mk 3 the second best. It's a great aircraft (I have flown it in RAF service and I'd like to hear those who dismiss it as 'wheezing' describe the performance of SK4!)
Much as my instinctive reaction is to side with the boys and girls at Benson who have made this aircraft a resounding success, if Defence is so strapped for cash and so forgetful of previous NAO reports on helicopter lift that it won't buy enough SH for both the SH force and the CHF then a Chinook/Puma SHF and Merlin CHF makes some sense to me. Also I am an admirer of 3 Cdo Bde, which manages to produce as much if not more in a 1 in 4 rotation as any Army unit does in a 1 in 5 (20% saving potential there perhaps?).
I must correct people who say the Merlin has the same 'footprint' as Chinook - although the dimensions are similar if you look at the area on the ground you need for the wheels and ramp, just have a look at where the rotor mast is - right in the middle of the Merlin, so the overall area taken up by the fuselage and the disc is actually not that much different from the Sea King - Chinook, with its rotors at the extremities of the fuselage needs a much bigger area. Downwash is bigger on Merlin than Sea King, but not as big as Chinook and over a smaller area (BERP affects this).
Also, I cannot agree more with a previous poster that marinisation is much more than just getting the blades to fold. Merlin is at least developed from a programme to produce a maritime helicopter - even if it doesn't use as much sealant as OG would like, there are designs for tiedown points etc as well blade fold, 3 hydraulic systems etc.
I loved flying the Merlin and I hope CHF do too.