can anyone please help me with the location of the relay for the rear window heater?
i have a mk1 60s so have no relay/fuse board in the glovebox

I'm not 100% sure that there is one. Is the fuse intact? Is the earth side of the circuit OK?

fuse is fine and earth is ok.
i'm getting a reading on the voltmeter but not the 12 volts required so i just assumed it was a dodgey relay

Usually relays will be on or off.

I'd take the readings with the connectors off.