Wonders will never cease! It appears that the Redmond brigade has at last done something about the PVR. Vista update KB950125 adds support for additional STBs and it appears that the PVR is now covered. When setting up TV signal select no remote control, scan down to Multichoice, select 1959 for TV1 and 1960 for TV2.
I only played with it for a while and it seems to working sort-of. It's not as reliable as a good set-up with the Dualview but at least it obviates that horrible learning process. Note that I have not buggered around (as yet) with the STB settings in the Registry - that's next up.
Suggest we pool our experiences to get to 100% reliable integration.