Apart from Pilkington and a couple of others in the UK, most tiles come from Spain or Italy by roadfreight. Tiles are dirt cheap out there and the DIY sheds buy up complete container loads to get them shipped over here at lowish cost. So many tiles you find at the DIY sheds, you won't find at the independent stores, who invariably buys from a tile distributor (someone else in the chain to take a 20% margin on the deal). In terms of quality, there are certainly some poor quality tiles at DIY sheds - look at the quality of the screen printing of the 'pattern' on the tile and see if you are happy with it - some look really naff to me. Otherwise, its surely a question of finding something you like, and if that is available at a DIY shed, I'd just go there.