The wiring on my buggy is all bespoke. I've got a query on the charging light when running a dynamo. I've tried following Pete's wiring diagram, but a bit confused over this. The charging light connects to 61 on the regulator, but is it powered from the regulator, or earthed through the regulator ?

Earthed, kind of.

You need to supply a positive feed through the bulb to the regulator.  When the regulator isn't charging the battery then current can pass that way.  Once the regulator is charging, then there is a positive feed to that connection and that cancels out the other one to turn the light off.

Excellent, thanks