We have been seriously let down by a rogue tile trader. His tiler laid two incorrect limestone floor tiles yesterday afternoon and he has not returned to finish the job. I need to lift the tiles before the adhesive sets too hard. Any advice on how to do this without breaking the tiles gratefully received.

You will have to give more details than that ?
Adhesive used? are they grouted? Is it 2 tiles ? Sizes? or is it 2 rooms ?

I doubt you will lift the stone without breaking them though.

The adhesive is GranSet Fast set Flexible. There are only two tiles, one 900 x 500 and one 600 x 500. I suppose the adhesive title say's it all!

Also, the tiles I wish to take up are not grouted.

Fast setting would suggest they're already fixed solid, and flexible gear is ever tougher to be fair, due to the added polymers and whatnot.

Try getting a trowel under one if you can chip away at the adhesive on one edge, then try to lift it, you might find there's a chance they'll pull up okay.