Re-tiling A Previously Leaking Shower - Thinking Of Boarding It

[Checkmygrouting]

I found my shower was leaking slightly as I was getting damp patches downstairs. I'm thinking a lot of this was due to the nature of the tiles (possibly slightly porous and all the edges were unglazed?) plus the grouting hadn't been finished that well I don't believe.
The missus has decided she wants all the tiles off and the whole shower retiled (it's a walk in cubicle). I've removed the tiles from the opposite end to the shower fitting and they've removed the top layer of plaster. It's left the wall still with plaster on it but barely 2mm of it. I've started on the long wall and it looks like that's going to be the same. I'm guessing once I start on the shower end a lot of the lower tiles will just fall off along with most of the plaster.
I was toying with putting up aqua board at the shower end and maybe the long wall( the end wall never gets wet) but didn't want to lose space in the shower if I have to batten especially where the pipes come through(can they be extended forward?) .
Can i screw or stick boards straight to the existing wall?
Can I tile straight on to the end wall(away from the shower) if I seal it or should it be skimmed again first?

I just want to make sure it gets done properly so this problem doesn't recur

All advice gratefully received

Many thanks

 

[SJPurdy]

If water has been getting through the tiling then the plaster underneath has probably been weakened and should be removed/replaced.
If the walls are plasterboard then why not take it down and replace with waterproof tile backer board (correctly jointed/sealed) so that the dimensions of the room are not changed.
If walls are plastered brick/blockwork then to keep room same dimensions repair plaster to give flat surface and then apply a tanking system over it before tiling.

 

[Checkmygrouting]

Cheers, thanks for the advice. I think tht's the route I will go down. Is any one tanking system better than another or are they all pretty similar standard?

Cheers