Dukes Meadow is a really great, 9-hole course that is quick and easy to get to from Central London. It doesn't require a long haul out to the country or a full day committment for a round of golf. I tend to shy away from golf becasue of the significant time committment, but I will defintiely play here again since we got through a round with 3 guys in just over an hour. Its inexpensive, as far as golf goes, and they have a decent bar and a place to eat after your round. They also have a nice practice range and indoor/outdoor tennis facilities.
Make sure you have golf shoes and a set of clubs or else they won't let you on. Don't try and sneak on with tennis shoes since they fully inspect your kit prior to the first tee.