I'll keep this short. Details changed as outing.
Getting a space in my house tiled and I paid my builder X amount for the tiles I chose, and he said one pack of these tiles should be enough to cover the space required. When he picks up the pack he realises theyre smaller than the size of a standard pack and therefore he needs to buy another 0.5 pack to cover the area I need, and as the tiles are expensive this means a significant increase in cost. He just bought the tiles rather than giving me the opportunity to choose another style which would have come in a larger pack and would have reduced the price.
Am I entitled to ask to see a receipt to ensure he isn't arbitrarily hiking the price up and to make sure there definitely was a purchase of an extra 0.5 set of tiles? FYI he has been quite shifty and has now asked for more money before the job has been completed which I've never had from any other tradesman.