Send clowns
Think we are coming at it from 2 different ways but see things the same. I am guessing that the people you are seeing taking additional work for the CPL have "burnt holes in the sky" in the US. I have been very careful to stay clear of this approach and for instance did my IMC in the UK not so long ago. Then went to US to reinforce those skills ahead of embarking on CPL/IR. Read a lot on pprune and spoke to instructors before going so made use of my time in the air and put myself through the hoops doing things like VOR/NDB (when I could find one!!) tracking/fixing, time enroute calcs, ETA calcs, fuel burns, nailing the altitudes and headings that I flew at etc. Also took flight following whenever I could get it and on a few ocassions received radar vectors when I happened to be passing through busier airspace which made things more challenging and interesting. The entire aim was to keep my skills honed and not slip into bad habits like I hear so often other pilots do.
As to first job flying into the US, I didn't think I was implying this. But you should expect to fly outside of the UK and therefore get exposed to different ATC and therefore I see no reason why we shouldn't be exposed to this at an early stage in our training rather than later on. Flying and working with ATC in the US or anywhere for that matter gives you the experience of different accents and even languages which will be one of the challenges we will face in the future.
I agree about your point on hours and would not be so naive as to end up with a logbook full of predominantly US hours. Ultimately though the cost savings are to lucrative to avoid and I am guessing that my logbook will probably end up with 2/3 US time with the rest UK. Lets say that when you start applying for jobs you have for arguments sake 500-600 hours then I reckon 1/3 of that in the UK would still be reasonable but am open to speculation on this and closer to the time if necessary will ensure the balance suits as market conditions dictate.