Comment on Damp Proofing a Basement by Adding a Damp Proof Membrane (DPM) by MCH.

I’ve read your tanking solution. I like your dedication. Possible bad news – did you consider that you will cause condensation. Basically the water vapour in the warm air in your habitable space makes its way through the plasterboard, through the quilt insulation and can condense on the cold black plastic that sits against your outer wall. The condensation will then run down to the bottom of the plastic sheet where it can appear as if there is a leak.
If you do a condensation risk analysis using freely available software like builddesk you’ll see my point. The solution is to have a vapour barrier on the warm side of the insulation. Pay particular attention to electrical outlets etc, the membrane should pass behind then and any holes for cables be sealed.
Because the vapour barrier is on the warm side of your insulation the surface temperature of it will not allow condensation to form.

A further comment on the outside of the wall – if you can get to it – place a geotextile membrane against the wall, then some gravel. If water gets to it, it can drain away to the bottom – where of course you may still have to deal with it or encourage it to run to a natural sump.