The cheapest places are like Leroy Merlin and Castorama but as I usually wanted in stock tiles and any variation on the norm was difficult to come buy and often difficult to source - and a lot of time looking at tiled boards which do not help much. A lot of tiles come from Spain and therefore a large order is usually needed by the shop or supplier before delivery. If you live in the south/south east there is a place in Carcassonne that sells tiles at a similar price to those in Spain as they have a factory there.
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