Tut Tut Welsh Dresser; how can you forget the name of a local shop.
On the point in question……you would be much better selling them on line on Ebay, Alibris, Abe or Amazon. Please bear in mind that the price that you have seen on Internet sites may be for specific editions and it might also represent the price that the seller would want to get…..not what they get.
There are several local places that buy books including places in Summerhil, Marchweil, Llangollen and Wrexham. At a guess, you’ll find that there will be little interest unless they are actually collectible.
Best of luck!