I'm renovating a small bathroom and want to tile onto a block wall
that has been finished with a sand/cement render. The 30 year old
plasterwork that was on has been removed - it more or less fell off.
The wall is out of plumb by about 1.5cm bottom to top, and surface
hollows of about 8mm over 2m. I don't think I'll get a good result
tiling onto it as-is

I was originally planning of getting a plasterer in, but was starting
to think about DIY as the final surface does not need to be perfect -
just good enough to take tiles.

What about using something like Ardex AM 100 "Rapid Hardening One Coat
Tiling Render" (http://www.ardex.co.uk/ardex_am100.asp) which
apparently will apply in 2mm-20mm in one coat. How hard is it for a
novice to get a decent result with this type of thing? The short
working time is a bit of a concern.

Another option would be to dot-and-dab 9.5mm plasterboard - but I will
lose more space this way - but it would be a lot easier.

Niall