Has anyone done/have experience of using a membrane system to tank a cellar?

It seems not to be a complicated process, but I haven't seen any details
from someone who has done it themselves and appearances can be deceptive

As cellar converstion costs seem to run around the £40K mark, and I have
a £20K budget, I'm thinking I could save a heavy amount by having the
underpinning and floor lowering done by a contractor but doing the
tanking and finishing myself.

Is this a viable route?