Homebase have 20% off using code DEC20, on top of 50% off tiles currently.
I've picked this example as I think it's a great buy, I got them a month back. Luna porcelain wall tiles, £13.99 at current offer, £11.19/pack (0.96sqm) after DEC20 code. Plus quidco/topcashback.
Other offers are Metro tiles at £11.18/sqm (two packs), which is almost as cheap as the £10 ebay offers but easier to return/pick up more and cheaper delivery.
Delivery is £3.95, normally a bit of a bummer having to pay delivery, but after having to pick up 28 packs of these in three runs it's probably a decent price.