Yes, length of lease is always a factor at the time of purchase. Even in 1996, the unexpired term was only 87yrs.
Whether the flat is still standing in 63yrs is not relevant to OP's question, however. Post #1 asks this:
I understand a little about lease extensions, that I've missed the 80 - 82 year window to extend under the conditions applicable and now would be subject to a marriage of its current value of around 100k
My question is what's the best course of action? I'm disappointed of course that I didn't notice this earlier and am reluctant to pay a large sum to extend considering its purchase price.
So would it be better to extend the lease, sell as it is. ( possibly at auction which is usually my choice) or pay off the loan and keep the property indefinitely.
The answer is surely that even a statutory lease extension (adding 90yrs to the term; reducing the ground rent to a peppercorn) would be worthwhile considering. The premium would involve paying only half of the marriage value element. The longer that OP leaves it before acting, the less the flat will be worth. It's already just about unsaleable and unmortgageable.