As it's ex-council, they would've probably done some works to bring the building up to the Decent Homes standard (think there was something like the Decent Homes Act 2010). Basically social/registered landlords were required to bring homes up to a certain standard, theoretically by 2010 but on our estate there were some delays as the whole estate was transferred from council to an ALMO (arms length management organisation), a housing association/housing trust.
They replaced wooden double-glazing with uPVC, installed cavity wall insulation, think they did loft insulation, all council tenants got new kitchens and bathrooms and the old inefficient and expensive to run back boiler (behind gas fire) and hot water tank systems were replaced with new combi-boiler central heating.
So depending on when your vendors bought the property from the council, some works might've been done in the past decade.
I had a roof replacement too.
I can't remember if I've me tioned it before in this thread, but legally, a freeholder has to serve a Section 20 Notice and consult leaseholders about any 'major works' that will cost more than £250. So you will get advance notice and you can ask them to show you the quotes.
Also, a recent legal case went to Court of Appeal, and freeholders now have to pay for an independent expert to advise leaseholders.
But if they don't serve notices and consult properly, the leaseholders contribution gets capped at £250.
If notices and consultation valid, if freeholder is council or housing association, they might offer interest free loan and leaseholder can pay in installments.