Thanks for the welcome and I have bought the car from a friend of mine who has had this problem for a while actually and told me it's a BIS thing! I have bled the red pipe at the front etc and pretty much feel like it's an everyday thing to top up the water. Friends wife boiled it once so head has been skimmed and I am confident it's not the head gasket again. Thermostat was junked ages ago so that is not an issue, fan is working OK. What bothers me is that the expansion bottle / filler cap seems to have no pressure integrity, as I say I can squeeze the big rad hoses and air goes in/out the filler cap without restriction - seems like the problem to me but want some expert back up!