Much easier to use
ebay's "Exclude" in their search function - they make it difficult to find and set-up, but once it's saved in your Favorite Searches, works pretty well.
With their Search box at the top of a page in the Stamps category, scroll all the way down the options on the left hand side to Categories/More Refinements/Seller/Only Show Items From/Specific Seller/Exclude and drop in a list of sellers you don't want to see (from a Word document, etc)
Of course, depending on how their servers are feeling that day, you might get an HTTP Error 502 but resending the request a few times always gets through. There is a limit on the number of exclusions but that changes regularly - I've excluded over 200 IDs.
Then you can save that search to your My
ebay Page under Saved Searches and directly click on it next time.
Steve Taylor
www.stephentaylor.co.uk