Sorry to pour fire on your water, Fireblade, but you cannot work in the UK on a FAA CPL, as the Air Navigation Order requires you to hold a JAA CPL and as far as I am aware this applies right across JAA land.
Furthermore, you cannot use a N Registered aircraft for commercial purposes in the UK without specific authority from the Department of Transport and, in a nutshell, you are not going to get it. Those couple of flying schools doing so have had these agreements in place for years but no newcomers are going to get one.
The N Reg Corporate aircraft operating in the UK do so privately, i.e. they are operated as privately owned aircraft. Their pilots require CPL's (JAA) as they are UK tax payers and are flying commercially for a living.
Also, I understand that current FAA regulations will not permit you to fly commercially outside the US in anything except N Registered aircraft but I wait to be corrected on that one. Saying that, there are many countries outside JAA land where they welcome FAA licence holders.
Also, if you are going for an Irish JAA Licence then you need an Irish medical not one issued by Gatwick, which would only apply if you were going for a UK JAA licence. Current UK Cl.1 medical = £ 337.
Rather than traumatise yourself wondering whether or not you are going to pass the Holmes Wright / Beynes Lantern Tests book yourself in at Gatwick (if you are going for UK Class 1) pay the £ 337 and ask to do the eyesight exam first. If you pass, woo hoo, all well and done but if you fail stop the medical there and you will be reimbursed £ 279 (ish). Or follow a similar path in Ireland. You can also hold a Cl.1 with deviation which restricts you to certain types of aerial work in daylight only.
Drop me a PM if you want any more info and I'll pass you my e-mail / telephone number.
All the best,
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