my cab cuts out 4 no reason

can any1 help me plz?
my car will cut out after about 10 mins running.  i am sure it is either the petrol pump or pick up in the top of the tank.  i've tried out the relay by listening for a click when the ignition is turned on (and the car has just cut out (as it won't start for about 10 mins and then fires up and runs sweetly) and the relay clicks into use.  i've also tried with a plug lead off when it has just cut out, and the plug fires correctly, so this must (i think)be down to fuel starvation. does any1 have any ideas what is wrong  and have the parts for sale that i need.

please hurry i can smell the sun coming out and i really need to pose
                  thanks loads Mansel

pm jamiegolf hes in wales