Main question is - how does one undo the rear driveshaft hub nuts when the beam is off the car?

Thanks,
Pavs

Airtool is easiest.

Alternatively you can put the driveshafts in a vice, but make sure it needs to be pretty solid.

chisel works if all else fails as does a grinder and chisel

impact wrench never fails for this sort of thing

Thanks chaps, will give the impact gun a go. Although all I've got is an Aldi jobbie and struggles with wheel nuts! Will also try the breaker bar and just shock it.

Could someone confirm which one is left-hand threaded?

Use a blowtorch on the nuts to melt out the nylon locking inserts. You would want to replace the hubnuts anyway.

Passenger side is left hand thread, notches in nut will confirm.

I ended up carefully cutting mine off with a hacksaw! I just couldn't get them to stay still in the vice and still have enough room to use a long bar.