Find out if you have anything valuable before you start. There are several publications in this area. Your library might have something, otherwise your local bookshop. Check ebay etc for more info.
You could try dealers at record fairs but obviously they have to resell so you may not get the best price. Some dealers also have shops.
hi you could try record collector either online or the hard copy mag.you will def get a rough guide to anything valuble or semi valuble .and sometimes in the back theres adverts for people that want full collections and general vinyl .worth a look
and if you have any fifties stuff i want first dibs lol
hope this helps