I've had the same problem, 900 hrs in the US, occasionally fly out of White Waltham when visiting. Assuming you're OK with the radio in the US (I fly out of Palo Alto, between San Francisco and San Jose, so no problem there for me anyway), it's not that big a deal. I did my first solo xc in the UK a couple of months ago. Occasionally I left things out that the UK wants (like origin of flight, no idea why they care but they do), they just very politely asked me for it. At W/W you definitely *do* need to use the radio, especially if you want to fly to points eastward and clip corners off the Heathrow Class A.
I did a couple of hours dual (had to anyway for the club checkout) which mostly got me straight on the different radio technique. The main differences are:
-- things have different names (Radar vs Center, Radio vs Tower etc)
-- the format of a flight following/FIS request
-- the format of an initial contact to an airport for landing
-- and flying-wise, the overhead join used in the UK
The smart thing to do (which I didn't) would be to jot down a summary of the differences and clip it to your kneeboard.
n5296s