Buy a share in a VW single seater. If you live in the South East then some of the costs will be out of proportion, but the figures do add up if you are flying lots. I'll illustrate with "worst case" figures based at an expensive airfield, but if you found a group based in a small field somewhere things get MUCH cheeper.
Initial outlay for share £1000
Monthly costs £50
Direct Hourly costs £13
Annual Flying Club membership £250
If you own a share for 2 years, flying just 6 hours a month and sell your share for the sum you purchased it you will have done about 140 hours for £3.5k or £25 per hour! You will not beat that without being sponsored! If you REALLY flew the pants off your new toy you could bring your flying costs down to £20per hour.
Forget the costs for the moment, you are flying for fun (aren't you?) and open cockpit, single seaters can also be excellent fun and great experience builders too. I should know, I've flown many if them over the last 10 years.
There is also a share available in the group I fly in if anyone wants to PM me