More like eau de fluxite!
Messed about with the tuner and got a picture. Slightly under focused with the pot at the end of its travel. Not great, but usable for what I need the set for this weekend, and in the longer term I can keep my eyes out for the correct tripler. I found three later Grundig ones in a junk box, one of which I may be able to modify.
There does seem to be a slight whiff of ozone coming off it but no sign of any arcing or other distress. Will keep under observation.