Tilly it's a new film but was written by Alan Bennett in 1999 and is a true story about a lady who parked on his drive. The lead was played by Maggie Smith in the original stage play.
Are you a fan of Radio 4? A radio adaptation of the original play was transmitted in 2009. Perhaps that's why you remember it? (You certainly can't remember the story from the book because there hasn't been one!)
There was a TV programme on about the woman in the van just a short story sort of thing -I can distinctly remember it being on and thinking i would get rid of the smelly old woman she was horrible ;-)
I've read the play and seen it on stage with Nicola McAwliffe as the lady in the van. I saw the film recently and loved it although I found it slightly funnier when i watched it live on stage. Great writer isn't he?