right guys i got the vaporiser changed today and now running on lpg without any overheating issues.
My point is! If you have lpg on your p38 and are having overheating/loss of coolant issues, check out your vaporiser before booking a new head gasket session. Its easy to diagnose. I just switched to petrol for a week to see. I also had to bypass the vaporiser but thats easy to do by just connecting the to vaporiser water pipes together. I also drained and bled cooling system. Had no overheating problems at all. Yes the car runs slightly hotter on the lpg but not overheating and not losing coolant. Also i suggest changing the grille on p38's as the orginal does not maximise air flow. I changed my grille at the weekend and now the car runs slightly cooler around town and the guage drops more when cruising on motorway. The further i am away from overheating the better. Got a lot of towing ahead of me this summer.