Next time you’re in search of a specific book, try these links:
From this page, you can download a PDF file of what books they have for sale at the moment. You don’t have to be a member to buy from them.
http://www.smplace.co.uk/sfr_cat.htm. Go to the Book section from the left hand column, you’ll find a link to their list of used and second hand books.
And yet another source of second hand books:
I’ve never dealt with them personally, but they have an amazing range of second hand books for sale!
The list on the web site may be out of date, but contact her anyway.