Bathroom renovation - how to best prepare for tiling

[AFT4B]

I have stripped our bathroom back to bare walls - removing the sand and cement plaster. We need to run new copper and waste pipework - both of which will come up through the floor, for all of the bathroom furniture and will likely be tight up against the wall. Two of the walls are bare brick and two walls are stud work.

What is the best approach to get to a suitable base for tiling (whilst hiding the pipework) from here? Ideally with minimal wall build up.

1a) plasterboard and skim

2a) dot and dab tile backer board
2b) baton and mechanical fix tile backer board

3) something else?

 

[Wayners]

I don't know much about this but I'd be looking at 30mm or thicker Abacus Elements boards. You need it well insulated to stop condensation.
You can tile or plaster over Abacus Elements boards. Something to start looking at.
Pipes running behind

 

[AFT4B]

I don't know much about this but I'd be looking at 30mm or thicker Abacus Elements boards. You need it well insulated to stop condensation.
You can tile or plaster over Abacus Elements boards. Something to start looking at.
Pipes running behind

Doesn't 30mm seem a bit excessive? Given previously it would have been tiles directly on top sand cement plaster?

I was thinking 12mm dot and dab or stuck with polyurethane glue and then mechanical fixings.