Nobody knows what individual airlines want anymore I'm afraid. Criteria differs from employer to employer. The CPL is really just a stricter PPL so training for it in the US is no big deal and I would recommend it because you will need VFR weather and doing it in the UK can get very pricey and drawn out.
The initial IR training can be done in Florida but the test must be completed here. The usual way is to do 25 hours in a single and 5 in a the twin in Florida. Then return for 10 in the UK sim and 10 in the twin. I opted for 20 hours total in the US, 15 on the aircraft and 15 in the sim. Never underestimate the sim because a good sim instructor can save you thousands.
As for the RT procedures in the US differing from the UK: this is quite true but not a huge concern. Doing all your training in the UK will take longer, cost more money and will ultimately be more soul destroying. The industry is less efficient here.
VFE.