Whilst nearly all clubs just charge for flying time, worked in the various ways described, the other thing to watch out for, especially at weekends, is a minimum rental time, i.e. if you take it for the whole weekend and just go to a flyin and back with half an hour each way (1 hour total) you would still have to pay the minimum of (say) 3 hours/day - one definite advantage of being in a smallish group instead of hiring from a club!
