Handmade tiles not flat

[Bubblecraft]

I know what you mean. This is why I don't stagger joints on brick effect tiles as it gives this optical illusion. Lovely work though & nice tiles!

 

[beanz]

I've tiled a splash back in hand made brick sized tiles.. Can't tell you who made them, as I didn't supply, but can tell you it took me 3 times longer to tile, and get them even close to no lippage. It's possible, but a LOT of extra work. What you need to ask yourself, is would you be prepared to pay 3 times the labour costs?
really your tiler should've given you the option, when he realised what a pig these tiles are to work with.

 

[Qwerty]

No curve mate, it's a trick on the eye caused by the pattern in the tiles

Don't worry it doesn't look like that in real life, only in that photo for some weird reason!!!