Good new battery and disconnect the earth from the battery will help stop draining the battery, I'm sure it will make it to show, they are pretty reliable cars, my wifes newer VW's cars always seem to break down more (usually some sensor goes wrong!!) than my old Mk1 Scirocco or my daily drive, Mk1 Golf (50 mile commute to work each day).
I can understand why you do want to sell as cars don't like just sitting there for long periods of time especially outside.
What ever you decide you have done a cracking job on the "old girl" and I'm sure you will have no problem selling it as it looks sooooo good.
Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
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