Just a side point...vehicles are VERY EXPENSIVE here in the UK. Pricing is about double what you can expect to pay in the US for a comparable used car. In other words, if a used car were to sell for, say $3,000 in the states, it will sell for about £3,000 here -- which makes it cost nearly $6,000. In fact, pretty much everything in the UK has a price that is similar to what it costs in the states, only in Pounds, which makes the actual price to us Yanks double.
I think it's valuable to have a right-hand-drive car here for a number of reasons (safety, first and foremost), but if you want to be "fiscally" responsible bring your own car. As mentioned, everything here from the road lanes to the parking spaces are much smaller here. I drive a Ford Mondeo (same as the Ford Contour in the states from the late 90s) and that is comparatively a larger car that sometimes I can't even fit into parking spaces lengthwise (sts).
You can buy as much gas on base as you want...you are restricted on how many coupons for off-base fuel you can buy. So, a drive to Scotland can be made from Lakenheath/Mildenhall if you plan your fuel stops very carefully (and can make 400+ miles on one tank), otherwise you'll have to fill up on the $8/gallon economy.