I got six months worth of blood pressure meds before I came over -- which, incidentally, cost me a flipping FORTUNE. Blue Cross won't provide that much at once, so I had to stick my hand in my pocket. The nice pharmacist gave me a card for their local 'frequent fllyer' plan and saved me a couple of hundred bucks, but it was still pretty painful.
Anyhow, finding a doctor in the UK and getting new prescriptions was easier than expected, though there was a bit of kerfuffle. Blood tests and the like. Also, the medications are a slightly different composition, so we had to try them out and re-test a couple of times.