I wouldn't worry about the weather in the UK. I did the vast majority of my training in this country, including hour-building, and I'd say I missed a flight due to weather maybe 10 times. And if anything, the variable weather conditions will serve you well in reading the weather conditions. I did have to turn back from cross country flights a number of times due to deteriorating weather, but it gave me the confidence to do so.
The FTO I will recommend time and again is Airways Flight Training in Exeter. All the instructors are ex-RAF and ex-airline. The CFI, was even a training captain on the Tristar at Cathay Pacific. Their standards are extremely high, and they will do whatever it takes to get you to that level. They're not money-grabbing, either. Their prices are very reasonable, and they don't expect payment for training until after your skill test (they don't want to add any unnecessary pressure whilst you're training). And they are very friendly. You'll be warmly welcomed each morning with an offer of tea, coffee and biscuits.
Have a look at their website, then give Brian a call. He'll answer any questions you may have.