It is NOT a VW But A VAUXHALL VECTRA 2.0. Hi there

Sounds like it could be head gasket, but before you do that, try a few things to confirm it is a head gasket.
Remove rad cap when engine cool, top up coolant, and start engine with Heater ON, and observe what happens, and add coolant as/if needed while engine warms up. when engine reaches normal operating temperature, thermostat should open and coolant will begin to flow good into top of rad. Shortly after that, your cooling fan should come on, to cool what just came into the rad. Then thermostat will open when it reaches temperature in engine again, and cycle begins again. Make sure that fan comes on after hot coolant returns to rad. While watching for flow during thermostat opening, also look for excessive bubbles in rad, indicating possible head gasket leak. If that fan doesn't come on at least by 2nd time thermostat opens, then I'd look into why not. If it does come on as it should, then I'd take vehicle to a rad shop that has dye they can add to coolant, and use a black light to see if it's coming out the tailpipe, that will confirm whether head gasket is leaking into cylinders or not. At least then you know for sure before tearing engine down.