I think I'll buy this 50% share of a 150 I found so I'll be learning in that.
Ben,
I'm not sure that that's a good idea.
I have a share in a C150, so I know about them. With full fuel, enough for three and a half hours flying, we can carry the equivalent of two twelve stone people. OK, individual aircraft vary a little, but that's a good ballpark figure. But that means if you weigh sixteen and half stone, your instructor would need to be seven and a half stone or less! OK, you may say, why not carry less fuel? Well, you can. But most C150 fuel gauges aren't very accurate, and neither is dipping the tanks. So most people tend to fill the tanks; it's easier and safer. Also, the numbers still won't really work out. A gallon of fuel weighs approximately 6lbs. For you to carry yourself and an average size instructor - say, 12 stone - you'd need about ten gallons less than the maximum...if my mental arithmatic is wrong due to fatigue, let me know, but I think that's right. That leaves you with around 10 gallons, or one and a half hours of flying time (assuming half an hour of fuel for emergencies). Now, that'll be OK in the early days, and in the circuit, but what about when you need to go on longer cross countries? And when you've got your PPL, and want to take a friend and fly to another airfield....maybe two hours away? And I haven't allowed for headsets, flight bags, winter jackets, spare oil, tie down kit, etc. And while you can fly slightly overweight without dire consequences - and many schools do - it invalidates your insurance, and is positively dangerous on hot days or short runways.
Here endeth your first lesson on weight and balance. And it also proves my point about not buying anything yet. You may be going to lose weight, but even so, this doesn't seem like a good idea. Don't do it Ben!