Fail to prepare, prepare to fail.
All the walls need to be + or - 4mm over a 2m length.
You’ll struggle if these Building Regulations for tiling are not met.
Sad news that another British manufacturer bites the dust with job losses, but I have to say that in my experience, the quality of their ceramic tiles is sketchy:
I’ve been asked to fix exactly the same tile for 2 different customers 2 years apart. One set were fine, the other set were bowed...