This morning, the airline have decided there was no lightning strike after all, although they are not yet offering an explanation of what happened to the electrics. To be fair, there was a fair bit of lightning activity around the South coast at the time. I was a bit surprised at the company's explanation of the decision to abandon a diversion to Southampton because it would mean flying back into the storms. Returning to Guernsey would also involve flying back through the storms as they appeared to be very active over that part of the Channel.
Guernsey plane U-turn not caused by 'lightning strike' - BBC News