I am at a total loss as to what the previous caretaker had written on the car. Since I am not familiar with the speak...
BOL----- what is the rest?
Remember, you're fighting for this woman's honor...which is probably more than she ever did.
I don't know for sure, this is just an educated guess based on watching other Britcoms, but I've always thought the word was "bollocks".
You can do a web search on that word along with "English slang", and see if you think it matches up with the context on the show.
If someone does know for sure what the word is, please correct me if I'm wrong.