I spoke to AlienOcean - they agreed that I need a sensorless controller for the new motor. But they don't have one.
So I went to here and forked out £22 for their sensorless controller. I seem to be delving deeper into the internals of electric bikes than I'd intended!
Apparently, sensorless is better than with sensors; the chap at AlienOcean said that motors without sensors are more reliable and more efficient (more miles per kilowatt). That makes sense; there's less that can go wrong.
I've had a controller go west on me in the past (with a smell of burning), but if they're only £22 to replace, that's no biggie. To put the cost of running a bike into perspective, I keep remembering that a tank of petrol costs me £80 and that is good for only two caching trips.
No caching for me today, I had to give my routine blood sample; they check how runny it is and adjust my Warfarin dose accordingly. I've been on the same dose, 7 mg, for 15 years now, but they still need to check it every three months. Plus, the weather is *very* hot, so a cool day indoors sounds good.
Some more work on the bike with the new Chinese wheel; I had put the controller in the battery bag, but on second thoughts, that will tend to insulate it and it might overheat. So I've redone how it's fixed. The controller is now bolted on to the back carrier, and open to the air. The leads are now wrapped in bubblewrap and sealed in with duct tape; there's no heat to worry about there.