I work 2 different logbooks. I have an official BGA book for my gliding time and a JAR FCL book for my power flying.
You are of course only legally obliged to keep a record of your flying time, it doesnt state anywhere in what type of format that should be. You could in theory write your hours on the back of a fag packet and it wouldnt matter.
Best advice however, get a BGA logbook(its not expensive, just a paperback) as your gliding time will be recorded much more logically and sensibly, especially if you pitch up at another club and want to fly one of their aircraft.