I used to live round the corner from Riley Upholstery at 233 Blackstock Road. I never got as far as getting the work done but they were very helpful when I was looking at options and would have happily used them - the quality of the work in the shopfront looked good. Don't know about collection and return though.
John Lawler has an Upholstery Shop in Hornsey and he collects and delivers locally for free. I don't know whether he is cheap but I know he does a good job. He also does Saturday classes so watch he doesn't recruit you as a student like he did with me
He is on 0208 347 5437.