Your thermo-coupling seems naff,you shouldn't touch gas bits yourself as it is dangerous and invalidates your home insurance,but you may be to trigger happy,where the flame is there will be a wire across the flame,this must heat up and glow,that is what keeps the gas valve open,let the wire heat up.
anon
December 2009
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.