o.k so as long as I leave the GEM alone and just swop the ECU over and use the transponder chip from the key that come with the new ECU I should be o.k and wont need to code or pair anything ?

I think I've pretty much pinned this down to ECU or coil and I've found an ecu for £59 and the seller is going to throw in a genuine ford coil as well for free so I'm hoping that will be the end of it