Very educational - thank you all for the insights so far.

I quickly fired up the head this afternoon and the bulbs still light up so its worth proceeding with the rest of it now.

I have some wiring ahead of me as I'm missing the transformer/timer box that originally came with it. I can modify it to work from my existing timer though so all should be OK I think. It will be more of a hassle to organise venting the cooling fan I think though. Many thanks to the now unknown poster who mentioned that they had a pavelle 401 PDF - I found the comment and a link in an forum archive from 2006! It was still live and I snagged a copy which gave me great help in figuring out the original setup.

So if anyone ever needs it, I have a manual for both the Durst 401 and Durst Laborator L1000!!