Like I said already, that is much, MUCH more complicated.
You're opening up the proverbial can'o'worms/hornets nest.
Essentially, you can't do AOC Public Transport work in this country in an N-reg aircraft. So you can't be paid if you've got an FAA CPL(H) by working 'commercially'.
N-reg aircraft can be flown corporately (for the time being) in the UK but technically, I guess that you could be flying on a FAA PPL(H) for that work.
If you want to be a commercial pilot in the UK, you'll need (at least) a JAA CPL(H). But, of course, you won't get a job with just a CPL(H)...