Progress report
Wood: Sanded down some of one side and varnish has come away nicely without too much effort. Noticed some fungal blotches in places and tried lemon juice from a bottle without much luck. Will try the real thing when i've been shopping.
Condition of the timbers is excellent. The midrail on one side is missing 1/4 inch of the facing edge at one end but nothing a bit of sawdust and resin glue wouldn't fix. The rest is rock hard.
Interior: Carpets have been binned. Original Leyland seatbelts will be removed and offered for sale.
Metalwork: floor inside car has been scrubbed with steel brush and come up well. Slight delamination in small area above crossmember. surface rust over 10% of floor where paint has lifted.
Paintwork: Put T-cut on areas of roof and bonnet and they have come up a treat. Should be the same elsewhere with the exception of the front wings (of which I have replacements) and rear wing lip which is rusty.
Mechanical: No resistance in brake system. I will assume that after 33 years idle the master cylinder is kaput. The whole system will be replaced.
Engine freed up with very little effort from starting handle.
Note to self [must stop finding things to do].

Older and more confused than I could ever imagine possible.