So to update this, after a bit of research there are a couple of fuses under the passenger seat which are to do with cruise, park sensors and towing electrics, these were OK. Also under the drivers seat is the towing ecu which communicates with the park sensors so it knows there is a trailer attached, the electrical plug to this had become dislodged probably by the tyre compressor I keep under there. Clicked plug back into place and bingo, all fixed!