Most charities shops won't accept vinyl records, unless they realise that they're particularly rare, as they regard them as totally unsaleable. So, if charity shops can't even get, say, 50p for one, the chances you getting £50 must surely be absolutely nil!
If, unusually, you've got anything worth selling, try the following places to see if they're interested in buying. However don't expect to get a lot of money for them:
Vinyl Resting Place
3rd Floor Afflecks,
52 Church St,
Manchester
M4 1PW
Vinyl Exchange
18 Oldham St,
Manchester
M1 1JN
King Bee Records
519 Wilbraham Rd, Manchester
M21 0UF