p.savage
Unfortunately you need a PPL before you can start and sit your ATPL's.
Also, if your building time specifically to get your CPL/IR in the shortest possible time I personally fail to see the point of doing an IMC. Don't get me wrong, i'm not dismissing the merits of the IMC at all. If your planning on doing any serious amount of personal flying in the UK I would say it's virtually essential!
All i'm saying is if your planning on doing all your training and hour builing in the US up to your IR it seems pointless to have an IMC.
CBK