If you're allowed to sell it on eBay. then you can sell it on your website. Usually, if anything, the manufacturers/suppliers will not let you sell on eBay but are fine with you selling on a website. I've never heard of the opposite situation. Some suppliers don't like internet sales of any description and will insist on a B&M store, though these suppliers seem to be less prevalent nowadays.

If you're buying stock from a legitimate UK wholesaler then you can sell it, there is no need for "re-sell" rights, that's the purpose of the wholesaler selling it to you in the first place. If you're importing brand name goods, then the manufacturer may get their knickers in a twist due to you not sourcing from their authorised UK suppliers, but if you're dealing with those sorts of products you should check with the manufacturers first.

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Lawrence