Sounds like the crank sensor is failing, they tend to die when they get hot then recover as they cool, but obviously can't say for sure. Relatively cheap and easy to fit DIY for a decent home mechanic.
DO NOT buy cheap ebay sensors, it is too often a false economy, better to buy a quality part even if it costs more.
Try
www.autovaux.co.uk
www.vauxhallworldparts.com
Local motor factors
Vauxhall dealer parts dept. (very expensive but best quality if you get original Vx part)
Could possibly be fuel starvation caused by faulty fuel evap system/dirty filter/pump relay/pump etc. but 90% sure it'll be the crank sensor.
frank, March 2012
