All repaired now.
The thermostat was rubbing against the inside of the thermostat housing which eventually led to the formation of a tiny pin hole. Got a new gasket and housing for £13 with VAT from nissan as it was faster than going to the scrappy.
I also changed my points while I was there, car sounds much happier now! Luckly I have fitted after market elec ignition so the next change will not be for ages, and then it will only be due to mechanical wear.
Ed: You still selling that body kit to me?
Thanks
