Where abouts in SE London did you end up?? I'm more kent, sort of, ish?
You use metal filler for wheels mate, it's a real fucker to sand back, so don't use too much, whatever you do!
It's literally a case of sanding back the wheels until they are smooth, the harshness of the paper you use depends how bad the wheel condition is, i.e a perfect wheel could just be gone over with an 800 then primered, or to take out some harder scratches, a 600 then 800, or some deep harsh marks could be given a 100 then a 400, 800, obviously you only need to sand down the bad bits with the harsh paper, just have to essentially blend it in with the rest of the wheel.
Wheel's aren't too bad to do tbh, it's all in the prep, which does get boring! lol