OK, me and a mate managed to get the seat off last night - 1 of the catches is bent, so it took a bit of wrestling and finesse.
Anyway, took the tank off, and the petrol seems to be coming from the very back of the tank - near the part that is welded/stuck on to hold the tank in place - by the bolt infront of the seat.
Its not very much, but the occassional trickly when u move the tank around and it drips onto the frame and down onto the sidestand. Also the "prong" bit at the front that aligns the front of the tank underneath the key is bent towards the left.
Can this all be fixed, or does it mean a new tank is needed?
Not sure really. There is no visible damage, just the bent bit at the front of the tank and the fact that petrol will run onto my finger if i hold the rear part of the tank low down. Not much comes out atall in 1 go.