Pleased to report that I found some PG Tips in Edeka. So suitably fortified set about finishing the baseboard base right around the room. Joining up the two ends over the staircase I achieved a level join, it was a bit like the Channel tunnel joining in the middle with millimeter precision, except rather than champagne, I had a nice strong cup of tea.
The supports on the right in front of the staircase is ground level, so the viaduct and whole station will be 8.5cm above this. I temporarily mocked up the height of the running lines & station in the middle of the section over the stairs just to triple check that he heights are OK. Seem fine.
Next steps will be to print out the track plan full size (no problem with running out of paper, I bought 5 reams of German recycled paper by mistake for work, they have a green hue rather than brilliant white) and start cutting out / fixing the actual baseboard / trackbed on the storage side and then working out where the high level supports will go on the scenic side (on the right). Printing this all out in 1:1 from Anyrail is a bit of a chore, well sticking it all together is.
A few tweaks to the track plan which i'll update in the gallery section. Mainly pushing the station back 5cm so that I have a slightly easier job accessing the room from the stairs.