Beginning to tile bathroom

Hi, I'm new to any home improvement/DIY in general and was hoping to get information on a few questions to do with re-tiling my downstairs bathroom.

The situation is that I have started to remove my old tiles and have found that plaster is sticking to the tile completely; through methods of trying to take off the tiles without damage it's clear that I will need to replace the plaster completely afterwards. Any suggestions on the best plaster to use? And if so will I need to use primer too or can I just tile straight onto it?

New tiles are ceramic and 100x200mm if that helps with any more detail

Cheers

So you've bought all the tiles?

Reading about the bad walls, I would have suggested an alternative option.

No the new tiles have not been purchased yet, I just have them already picked out. Wall cladding sounds like a great idea as a replacement option though so cheers for that, I will do some research...

You'll find it's something that your local plumbing merchants will stock too; Bathroom fitters tend to buy them along with the bathroom suites when they refurbish the customers WC.