can you just unscrew this out and put another in without losing too much water? just wondered whether itsd a real quick job or you have to drain coolant system first?

Just screws out, should not loose any water. ;)

Just screws out, should not loose any water. ;)

sound - cheers bud!

removed it - cleaned it - realised I have no liquid/instant gasket - is the copper washer thats on it good enough or do I need proper gasket sealant?

 

Also. ..

 

Can you buy a new yellow plastic housing as mines broke.

Dont think you can get the plastic bit on its own, try putting it back on and see if it leaks, if it does then it wont be a major leak and you can take it off again and use another washer or some liquid gasket.