The dogs survived! Installation of the Time Step PSU was straightforward, but I left the transformer in-situ (the instructions suggest going the whole hog and removing it even though the mains cable is taken out). All is well, and a record is now playing. The presentation of the sound is immediately different - rather harder, I feel; however there are nuances and harmonics clearly audible that I cannot recall hearing before (even on my old HD Spacedeck). So, I shall leave it running for a few days before listening critically, by which time my J7 upgraded Technics arm should be here to add to the fun.
I took the opportunity to check the level of my OL armboard, and it was not level with the platter. A few minutes of cursing and fiddling with washers has fixed the problem. The change in the overall character of the sound is probably due to this rather than the Time Step PSU.
Next quest - suitable threaded adaptors to allow me to screw some Stillpoints into the Technics' chassis. Why do the Americans have to use archaic Imperial threads?
Update: Stillpoints balls locate quite nicely in the base of the SL-1210, with height adjustment provided by Stillpoints Inverse Risers - BIG difference in musical flow and overall enjoyment!