How high does the single ply go up under the tiles? That soil pipe looks like a right pigs ear, what happens to any water that gets into that little hole between the tile and the wall where the lead flashing ends on your 6th pic?
The single ply goes up approx 100mm behind the tiles, however they left the lead work around the soil stack and used liquid sealant. The quote was for the following:
"To replace any damaged or rotting boarding using 18mm BBA approved plywood and install SikaPlan single ply PVC membrane along with termination bars, drip detail around hopper, fixings, adhesive and SikaLastic detailing around pipe detail. All work to be carried out in accordance with the manufacturers specification. "
From my underatnding Sikalastic is just a general term for any number of products in that range, so not sure what Sikalastic detailing would consist of?
I can't find any info online to advise whether the work done is "in accordance with the manufacturers specification. " However a Sika representative will do a site visit to check the work and issue a 20 year guarantee.