Not sure if I can give you a specific answer, although I would like to pass on some information from my own recently research. Also, I am working on the basis you will be returning to the UK after you US training.
Recent changes in CAA/JAA regulations means that you will no loger get ANY exemptions at all on foreign ICAO IRs. This means a full cost of approx. £10k+ would be required for a JAA IR.
Therefore, if you are planning to return to the UK, you should seriously consider doing the CPL only and returning to the UK to to convert it and do the IR rating there.
