Cloud Surfer,
I did just that, CPL in the states and IR back here. I am ex-mil rotary so I am not a total 'newbie' but I found no difficulties in this at all.
You don't say where you got your 150hrs, but if they are in UK then you definitely have nothing to worry about. Nav/airspace etc in Florida is less complicated IMHO (not a lot of either about - vast open spaces), but the courses are still run to a JAA sylabus and standards with JAA instructors and examiners. IR is very different so it will be a change regardless.
The only real issue is if you do a ME/CPL on one ac type and your IR on another, but again that shouldn't really be a huge problem, some people have problems converting from a C150 to a C 170 - that is your call.
The biggest difference I found was one of over £2000 - even after flights, visa, accommodation etc had been taken into account.
Whichever way you go - good luck
