its only costing me £50 an hour
Don't forget to include hangarage (or outside parking), depreciation insurance and so on in your hourly cost. Parking (inside or out) is insanely expensive in the London area. It MIGHT even be cheaper to go further out - Conington's a good spot to begin. Start a spread sheet and put in ALL the costs associated with running an aircraft, include your projected annual hours and see which of your options are cheapest. If you do less than 50 hours a year, it's usually MUCH cheaper to rent from a school! Most people seem to hide their heads in the sand when it comes to costs of running a plane.
I still think the most cost-effective solution for your hours-building is a Cessna 150. Hourly fuel is 18 litres, comparable with most 'plastic fantastic' machines. It's far more robust than many permit aircraft and you can pick up quite a nice one for £15-20K. You'll get your money back when you're done with it. Maintenance is a little more, but not too bad if you can genuinely do some of it yourself. You can also do your night and possibly most of your IR(R) rating in it, too, an excellent way of gaining hours rather than just making holes in the sky.
I've been privileged to fly in a number of the noseleg permit aircraft around and most of them are less straightforward to fly than the C150. They might go quite a bit faster than a C150, but when you're hours-building, you're really NOT interested in speed, just time!
TOO