robin,
What aircraft are you refering to by a 'much cheaper' one? The whole idea behind this venture is that the more you fly the less you pay per hour, it wouldn't make sense for someone to join a group like this and only do 2 hours per month. If people wanted to do that fine, as all of the fixed and variable costs are already covered (minus fuel) so it's not costing the group anything if it's not flying. I myself would intend to fly at least 10 hours per month, costing me only £54 per hour. Compare this to renting out a clapped out old Cherokee 140 or 152 for £110 per hour. I know which one I would choose!
Ox