As idyllic as the buy the US OTS option sounds, the practicalities of politics get in the way. Remember our AH 1Ds had different engines (to keep UK suppliers and voters happy) but with the RTMs came a change in fuselage dynamics when the cannon was fired and Boeing wanted even more money to re-jig the fire computer algorithm so the cannon got more accurate instead of less as rounds were fired.
Then you had the fiasco of the AAC being forced to sign off delivery at Middle Wallop for a number of Apaches that were flown there, had the MFDs removed (because there was a shortage) and then driven back to Yeovil to be installed in the next one. Now, such shenanigans could also be experienced dealing with a UK or EU supplier but you can be pretty certain that the required UK spec for UH60 would be different from US spec and extra costs would be involved in modifying it.
Not sure what the perceived problem with Puma 2 is, most of the Puma 1 s foibles have been removed and although not a specialist in any particular area, manages a reasonable fist of most jobs it is asked to do.