The replacement rear wheel that I ordered from Ebay arrived - but I don't need it. I had a look at the wheel with the wobbly axle, and it turned out that (I think) all it needed was the axle nut to be tightened up a fraction, so that the ball bearings aren't s loose in the ballrace. Never mind - I put the full monty onto it (tape to protect the inner tube from the spokes, gel insert to absorb thorns penetrating the tire, puncture-resistant inner tube and Kevlar-reinforced puncture-resistant tire), and it's ready to roll. And all that puncture-resist stuff really works. I've never had a puncture while out since using this.
I had an idea about bike batteries. I'm putting together four 5 AH 14.8 volt batteries to make a single 10Ah, 29.6 volt battery pack. But thinking about this, I made it into a 10Ah because that's what my existing batteries are. There's no reason why I shouldn't make two 5Ah, 29.6 volt battery packs out of the same batteries, and the advantage of that is that it gives me a bit more flexibility. So when I'm going out, I can take 3 of these 5Ah with me, and when I get back to the car after the morning's biking, maybe one is empty and one is half-used. So for the afternoon, I can take 3 full 5AH and the half-full 5Ah, for example. If I use them made up into 10Ah packs, I couldn't do that.
So I've made up a driver cable suitable for a 5Ah, 29.6 volt battery pack. I can use the same charger cable as before.
Tomorrow I'm planning to go north of Royston; there's a few circuits there that I'd like to tackle.