I came unstuck in the same way, declaring SORN and then leaving the car in my parking space outside of the house whilst I worked on it. I was prosecuted and sent a letter of mitigation (not being driven, declared SORN, not a thoroughfare but parking space in a a cul de sac) but the result was always going to be a fine as I had to concede that it was defined as a public highway. Was fined plus costs which added up to just over £100 for two offences (seen twice in two days by Council Wardens). Phoned up and paid by card on receipt of the details. Mitigation may be taken into account as far as the fine goes, but I think that the offence is absolute.
I (or my wife as she was the RK

) never had to attend court and don't believe that you will either. Nor (as far as I am aware but stand to be corrected) will you have a Criminal Record - naturally is is recorded but does not need to be disclosed to prospective employers, nor does it affect US entry Visa waiver status.