Re: bad tradesman
Catch 22 - if you take the tiles down without giving him the chance to put it right, you may have no claim against his workmanship, but at least you have saved some of the tiles!
You ask for help but you've already made the decision and it's now a game of wills. If your not happy and you decide not to pay him - that's your choice. He may take you to court for non payment and lost earnings but you could counter claim for loss of materials and damage caused. You may both end up with some loss and that may be the best of a bad situation.
If all the tiling was complete, at what stage did you decide it was 'awful' and how long had the work been in progress? Have you contacted the person contracted to undertake the work with your proposals? Many questions and usually photos help to give advice, but in this case your actions have almost decided the outcome.
If it's of any consolation - I'd have taken them down as well if I'd not been happy, however I'd have asked him back ASAP to watch me take them off just so he knew I was not best pleased.
No doubt it will run.
Good Luck.