A couple more differences...

4x4 has heated washer jets
4x4 has a different shaped bonnet at the scuttle end
The 4x4 heater blower always runs, unless the right-hand knob is all the way down.
4x4's have small sapphire badges on the rear window plastics.

Facelift saphs (91) had single-colour rear spoilers (i.e. no black lip)

I'm sure there are loads more!

Neil.