Ok I figured out what was wrong. I am an idiot that's what. I inadvertently set the hot end PID parameters as the Bed Parameters in the config.g file.
Best posts made by KeithW
RE: Delta with New Duet 2 WiFi Only homing on y tower
So, although with a multimeter all tower switch connectors were testing closed at the board end once plugged in they were signalling open. I cut them off and crimped fresh ones and it is working now. Thanks