Have you read the book? How well did the movie treat it?
I think the film is actually an improvement on the book. It's funnier, more tightly constructed, and Woodbine Lizzie is much more compelling in the body of Julie Christie than she was on the page (seemed a bit crusty round the edges in the book, to me). Has anyone read Billy Liar on the Moon? More of the same really, Keith Waterhouse stealing from James Thurber... still, sort of amusing.
I read the book first and absolutely loved it. The film is a superb adaptation though and the only thing that I can remember that is really different is the ending. I doubt they could have found a better cast than Courtney, Rossiter, Christie, Bewes etc. as well.
The TV series (although I've only seen Series 1) is quite good but loses all the pathos of the film. It is very much a typical 1970s sitcom and although it is funny, the characters are not particularly believable.
When I read Billy Liar on the Moon, which was some time ago, I thought it was quite poor. In the first book Billy was young and it was easy to see things from his point of view. In the second book he just seems to be an unpleasant character. I also think that Reginald Perrin had stolen Keith Waterhouse's thunder a little as that is how a middle aged Billy could have behaved.
I read the book at school and watched the film soon after and it catches the spirit very well, although one bit of the book i was interested in was omitted from the film version.
Its that man again!!