Here are ways to find out what is selling well at eBay UK:
1) Check out the popular searches and most popular products on eBay UK:
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Popular searches: Link hidden: Login to view
Best selling products: Link hidden: Login to view
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2) Perform completed listings searches for products or brand names to see the conversion rate and average selling price.
To do a completed listings search, simply click the Advanced Search button next to the main eBay search box. Enter your search keywords as usual, and then check the Completed Listings box. Hit search and you'll see historical data for the previous 30 days. Successful items are in green; unsuccessful items are in red.
Please note that what is popular does not mean it will be the easiest to sell, because it is possible for a highly popular product to be over saturated and you will be facing a lot of competition. With the tools I have shared with you, it could help you get ideas on what niche product to get into. :)
Let us know once you have decided on a product to resell and we will help gather suppliers for you.
Hope that helps :) Let us know if there is anything else we can do to assist you.