Hi fellas thanks for the reply. Yes that mechanic didn't seem too sure. I went to a couple of mechanics today, both said it doesn't seem to be head gasket, because theres no white smoke coming out of the exhaust, no milky oil, no oil in the expansion tank and the water isn't being lost around town, just on long runs on the motorways/highways . They both said it could boil down to the following things, The cap on the expansion tank, water pump, thermostat, heater core. Right another question, the radiator fan isn't kicking in, I replaced the fan switch, and the number 30 fuse on top of the battery, then it started to work, but now it isn't working again, I pulled off the switch adapter connected to the fan switch, connected a wire to both connection points on the adapter and the fan started to work only whilst I had the wire connected, maybe I need to buy another new fan switch? And when the fan isn't kicking in, could this be the reason that the Overheating light comes on when there is water loss? Sorry for doing your heads in guys, I just don't know a great deal about cars. Thanks. And Yes it is a right hand drive. P.S one of the mechanics today said the windows are getting steamed because of a slight leak in the heater matrix (core) but that doesn't explain the great amount of water loss