The question about ceiling height related to the easy of re-selling it, OP, most people aren’t 5’! It’s hard to tell from the pictures. Even if you think you’ll spend the rest of your life there, it’s worth considering what would happen if you needed to sell.
This page explains why extending the lease gets more expensive after there are less than 80 years left:
www.moneysavingexpert.com/mortgages/extend-your-lease/#howmuch
There is a calculator here - you will need to know roughly what it would be worth if it didn’t have a short lease, so you’ll need to do some research on sold prices. You also need to know the ground rent because that is factored into the calculation: www.lease-advice.org/calculator/
Remember that if you buy it at 78 years there will only be 76 by the time you come to extend because you have to own it for two years first. All bear in mind potential house price increases over the next couple of years. There is more advice on that website too.
I thought the estimates PPs have made sounded a bit low so I plugged some values into the calculator - I tried £190K and £200K with an annual ground rent of £25 or £100. The calculator estimates £14-15K PLUS COSTS, which will be a few thousand - your own valuation and legal fees and those of the freeholder. In my experience the calculators are accurate because there is an underlying formula that’s used.
As others have said, a shorter lease affects the ability to mortgage - some lenders won’t lend below 75 years. Even if you get a mortgage to buy now you need to think about the possibility of remortgaging in the future and the possibility of future buyers getting a mortgage.
So basically yes, there are issues with buying a property with a short lease. If you have the money to extend it then the issues go away. Even if you expect to die in the flat there may be some reason to move in the future that you can’t imagine now - life changes!