Further to my previous post, the layout, dimensions and clearance are practically identical on both sides of the bottom bracket, so I can fix the magnet ring either directly onto the chainwheel (epoxy) or in the gap between chainwheel and BB, and locate the sensor on the frame member (with or without spacers).
I intend to mount the Power Pack low down at the front of the bike on a Brompton Block (Dahons have the appropriate fitting point) - a much more stability-friendly location than on the handlebars, and the cable run to the front hub is also shorter. The other cable from the Power Pack can then be run to the PAS along the base of the main frame member, rendering it almost invisible. In my opinion, nothing spoils the appearance of an electricified bicycle more than cables all over the place! And by the way, it's a fairly early Mu Uno with a coaster rear brake, so there is no unsightly rear brake cable.
Since I bought the bike, at least 10 years ago, I have made various small modifications to it, mainly to reduce excess weight. I think the first mod was to remove that unsightly plastic cover on the chain, and replace the silver-coloured chain with something a bit more appropriate. Next, I removed the prop stand and pump-in-the-seatpin, and replaced those ugly ergonomic handlebar grips with some plainer ones, as well as replacing the front brake lever with a dinky BMX-style one. I also took an inch or so off the length of the handlebars. Finally I replaced the lumpy-looking folding pedals with some better-looking ones (which also fold).
Other than that, the only modification I'm considering at the moment is to replace the rear wheel with one based on a Sturmey-Archer 2-speed coaster hub.