Don't bother with the IMC rating, go and get yourself an FAA IR, this will give the IMC for free. Plus the extra time on instruments will make you a far safer pilot....And its not much more than IMC rating.
Do it in California, and don't be fooled when people tell you that the weather is always too good. Have flown in all conditions over here.
If nothing else, once you have the FAA IR if you come to do the JAR IR you should be able to complete in minimum time (saving money in the long run), or you may decide to get the FAA CPL and CFI, build your hours, get the FAA ATPL and then convert. There's loads of options, and this way will certainly cost less than the 55,000GBP that OAT charge (and you only have a few hundred hours when you leave!)