Well the car is fixed. The ecu was OK, the diagnostics found no comms with gateway module. (all alien to me). 3 fuses replaced as the head unit was out as well and everything seems to be hunky dorey. Had the m.o t done as well which showed the offside brake light has failed probably due to the electrical issue. Ordered a complete unit from Paul (lsd). Total cost including the m.o.t. due to my stupidity £616. Could be worse 😭 oh it was...£15 extra for new jump leads!