Almost agree with FFF,
Do the full FAA IR in the states, this will give you a much larger selection of FTO's to choose from as you won't HAVE to go to a CAA approved school.
This will give you the UK IMC rating by paying (surprise, surprise) to have the CAA use a HP Laserjet to re-print your license on incredibly expensive A4 paper
Then as FFF says, this won't prepare you 100% for the problems you will face flying IMC in uncontrolled airspace in the UK.
Either pay an instructor to "put you through the mill" or buddy up with somebody for at least the first couple of flights when you get back.
I think this way will prepare you much more for intentional flying in IMC.
BTW I have an FAA IR but don't really use the IMC privileges as I am not a big proponent of the "Big sky theory" (do a search) which is sometimes required (especially at weekends) if Radar is not available to you.