ok update on my Astra. Fan is working thermostat works (replaced). temp sits at 85 . garage said i had a porous block, so they used engine sealant. this has made the back pressure a lot worse. Loosing water out of the expansion tank more quickly than before. Sounds like a blockage to me and adding this solution has added to this. I could be wrong, the garage has got it back. will keep you informed. Anyones advice is welcome. thanks to everyones input and merry christmas.
sounds to me like a stupid mistake on the part of the garage that has replaced the head gasket on these 2 cars , my diagnosis is that the head gasket has been fitted upside down , this will cause one of the waterways between the block and the head to be blocked off , the car will act normally but will pressurize the water system causing coolant loss through the header tank , needs to be rectified as this can also cause hotspots within the engine leading to head gasket failiure again!!