Novice-replacing tiles ensuite

[MisterMcGoo]

Hello,
Novice DIY tiler here looking for advice please. I'm replacing tiles in very small upstairs ensuite toilet (floor area 2 m squared). They were put direct onto plywood (by another) 15 years ago and have cracked over the years. I'm in process of removing adhesive. Sink and toilet have been removed. Skirting (onto mostly stud walls) wasn't removed during original job.

I was thinking i could install 6mm cement board over existing ply and raise the floor level and raise the fixtures the extra fraction?
Will the layer of adhesive under the cement board make up for any unevenness in the different ply boards?

What are my easier/better options? If i didn't want to increase is my only option to remove existing ply and put down thinner layer along with cement board, which seems like a more hassle.

Also, would people normally go to bother of removing skirting for such a small area?

Thanks

 

[Kastar UK]

Depends if forms a trip hazard at the door with the extra height
Will take 10 mins to bar up the ply , tiles go under skirting so probably needs to come off, i screw down cement boards screws every 200mm.
Doesnt matter about uneven will get that with adhesive doing the tiling so long as is within adhesive depth guides . Just remove any big lumps of old adhesive before offering the cement boards