Despite your honest belief you have done nothing wrong, I am afraid that even though you personally had insurance, as you let the potential buyer out without checking he was insured to ride, then you are guilty of permitting him to ride without insurance.
The law relating to insurance is very strict, and there is no defence in this case. The Court could sentence you by way of 6 to 8 penalty points, or a possible disqualification. This is in addition to a fine and court costs. As such, my advice would be to plead guilty and try and obtain the lowest sentence possible.
As for the eBay chap, I hope you got the money off him for the now bent bike. He can also expect to be ‘stuck on’ for riding without insurance as well as careless driving.
Motorcycle Monthly March 2014