This is a preliminary detail for a new insulated slab and EWI to an existing floor (in this are we'll be removing an existing suspended timber floor).

What should I do about the DPM, chase it into the wall or something (I can't see a DPC in the existing wall)? And what about airtightness, what should I be doing to the plaster where it meets the floor?

Any other pointers?

Cant see a great deal between them, maybe a little less work in below slab insulation as less concrete to pour and only 1 pour

Try to extend land drain down to base of wall this will reduce moisture at that depth and reduce damp in the wall.trying to retrofit dpc will be expensive and awkward, so housing your dpm into wall 1 inch will acheive nothing i would sandwich your dpm against a cleaned wall with the floor battens and seal behind with a good mastic making sure you get a good compession of batten mastic and dpm that could act as your airtightness if the internal render could be made good to battens?

noticed you spec phenolic insulation for EWI, not sure that phenolic can be used in this way? isnt it wrapped in foil? would adhesive work on foil backing? also i hear it detearate after time so i would use it at all.