Two weeks in...
Well after my purchase, I've got down to some triage and work.
Palmers in Hemel did an inspection, and came up with:
Fusebox melted - explains the schitzo electrics, no wipers, no rear-screen heater, etc...
Heater fan inoperative.
Brake fluid contaminated.
All discs and pads corroded - £1000 to replace.
O/S/R upper ball joint arm worn – £505.86 + £160 labour
N/S/R lower radius arm worn – £384.00 + £160 labour
Suddenly my £700 purchase has the potential to become a mortgage breaker. So I'm going to do the work myself with your help. And a big thanks for the invaluable advice on the forum. (My local garage has quoted £520 inclusive for the brakes... crazy mark-up by Alfa)
Heater repaired - was seized, now absolutely fine.
Electric windows repaired - coroded contacts.
Wipers and water jets fixed - cable-ties are handy!
Recon fusebox arrives tomorrow - £70 ebay
And will try that rear-heater DIY relay fix at the weekend.
Thanks again all!