The BA has three wires attached to the demister/rear window 1 on the drivers side which is attached to a lug and 2 on the passenger side the top is the antenna which is stuck directly to the demister/windscreen and a wire below that which is attached to the windscreen/demister directly, this one has come off and needs to be reattached. How do i reattach the wire to the windscreen again as i tried it with tape just to see if it gave power and the tape got very hot.

An OLD fix for breaks in demister screens was Nail Polish, silver preferably. Many years ago when they were just stuck onto the glass, Ford had a repair kit for it but I doubt that it is still available.
Short of this, try and see if you can find something in an after market parts store, or maybe talk to Obrien glass?

reasonable success with demister repair kit (normally 2 part similar to araldite but conductive) should be available from supercheap/repco or similar .
allow time to dry properly !