Hi most of the minor electric faults that crop up are earth related- the ingress of moisture and creeping corrosion eventually get to the point where the earth connection isn't allowing electric back to battery. Quick test is a bit of wire from existibg earth pointtoching against a clean bolt in chassis if lights are restored you just need to clean up existing connections and possibly add a few more decent earth cables to key components
Maplins sell some gel called contralube which we have used on 4WD vehicles and ageing kit cars usinng mk2 escort looms about same age and "quality" as the leyland item in tr7, it improves conductivity and prevents further corrosion. I'm currently working on similar issues myself
And use contralube on switch contacts joints, cabble ends as well as in bulb holders etc
A good bit of kit for testing components in situ is a Sealey power prbe that allows you to power up componts in stu as well as indicating polarity of a coonection etc
Hth
Mike
Near Penrith and the Lake District
