Kinda goin on for a while now but really starting to annoy me!!

My UK 2000 has the M30 fitted, within the past 6 months its playing up. If I leave work and call into the local petol station (approx 2 miles from work) for a fill up, I use the pump, lock the car using the keybob. Go in and pay, come straight back out, disarm the alarm, get in turn the key, reds come up but absolutly nothing happens, no turn over, nothin...

However, if I re-arm the car with me in it, sit for 5-10 minutes, dis-arm put the key in and bingo.. its starts.

If I did a 10, 30, or 50 mile journey, it does the same thing.

If I moved the car out of the driveway, locked it and got back in 2 mins later, it works.

It isnt specific to any local.. could happen at mates houses, shops, bank, anywhere....

Any ideas folks as its really annoying now!!