Hi changing our bath from a freestanding roll top to a more traditional one. Now hte chances of the walls being square are nil. I'm going to have to remove the tiles below the level of the new bath so I'll probably have to cut the tiles in place. What's the best tool for the job, I could try and remove the tiles then cut them and refit them. Chance of getting the same tiles are nil so I don't want to end up having to retile the whole bathroom.

Any help appreciated.

Start at the bottom where it doesn't matter so much.

Smash one off carefully using hammer/old wood chisel.

Then try to get behind the rest with a strong scraper and hammer.
If they pop off, they've been fixed with tubbed adhesive and you'll be fine getting the rest off. If they break and won't come off in one piece, then they have been fixed with powdered adhesive and you've no chance.

If the latter, you will need to trim the tiles in situ with a straight edge and angle grinder with a diamond blade. It WILL be very dusty. Test fit the bath several times first to make sure you get it right.
Silicone the bath rim to the wall where the old tiles where very heavily and mechanically fix also. Then finish the tile/bath with Dow 785 sanitary silicone.

don't forget to fill the bath before sealing, otherwise it will sag when you fill it for use and pull the seal apart.

It doesn't if you use proper silicone and fit a good quality bath. Cheap nasty ones will flex, but a decent 8mm fully encapsulated one won't move a bit.
I usually put a frame around anyway made out of 25mm x 25mm timber.

was going to fit a frame for support as well, normally part fill the bath before siliconing just in case though.

Toying with getting an Exakt saw and some extra discs for cutting the tiles.

Fix batten to wall at right height as a guide. Run along the wall with an angle grinder, diamond blade, and cut through tiles and about 10mm into wall. Smash off the tiles with ease. It is very unlikely that the new bath height will fall on a joint!

top tip – when the new bath is in, if you are putting in panels or boxing it in, then pack around it with Rockwool. I have always done that and the bathwater keeps warm for hours.

C

Great tip on the Rockwool Chris!

I could try and remove the tiles then cut them and refit them

Best option…I assume you only need to refit the ones around the base of the new bath? You can wreck plenty of the others, then just use a sharpish chisel and ease out the last two lines (so you have spare). Then cut them when the new bath is in.

If yo have any tradey mates with one of these, it would do the job…