Not wishing to add to the puddle of pi55 but Flying Paddies advice does have a ring of truth to it but is perhaps not the most practical route for most. The CPL training and test can be conducted in the States but when it comes to the IR you must take the test in UK airspace. The most common plan is to return and do the remaining 10 hours of training in the UK.
Having experienced about the worst disruption the UK weather could throw I must say that if you want to get a CPL done in minimum hours and time then look for sunnier climes. The CPL is even more of a glorified PPL now as the start of the new year saw the IMC part of the test abolished. You will want good visibility and ideally a cloud base of +2000FT AGL when training for your CPL. You have more chance of pi55ing in the Queens handbag than getting a good run like that during the UK winter depending on where you are!
The RT may be more challenging and ultimately more rewarding in the UK but this is something you can get the hang of within a few hours of flying here. The US is more relaxed in every aspect of flying but to state a CPL trained for in US is somehow less credible than a UK one is slightly naive. I don't think employers will be too fussed one way or t'other but who knows what they want these days.....
VFE.