Wow brill, thanks so much everyone for the great advice.
I am now circling (like a bird of prey) a new property which I would like to make an offer on.
It's more money than the last one (offers over £85,000) but according to the Home Report, no great big enormous 'mysteries' which my Dad has to uncover to find a total disaster.
Re the last flat, although a leak may well be fixable for a reasonable amount of money, the other problem was that the building had no factor - sometimes this is good (factors can be a racket) but sometimes this is bad. A friend of a friend bought a property in London with no factor. Is now having to organise roof repairs, which involves tracking down all 7 other flat owners, 2 of whom have gone AWOL. The remaining owners are refusing to split the costs to miss out the missing owners. Basically, it's down to him to negotiate, organise, get court orders if required, before he can get any work done.
The leak on the last propery I looked at apparently might have been coming from bathrooms in flats above (waste water leaking). With no factor, it could have been a bit of a nightmare.
So I ran away.
Anyway, new flat now in sight, parents have agreed to go through the whole rigmarole of viewing again, finding potential disasters, etc.
It needs nothing doing inside, although, @Midcenturymater I'm sorry to say, it's 110 years old. Eep.
I'll let you guys know.
In news more realted to my original question - I've been filling my (small) bedroom with bags full of charity shop homeware. I don't have any room to store furniture (apart from that chair I found in the street) so just now I look like someone with a serious hoarding problem.
It's been AMAZING though - I aim for £1 or less per item, and will post a list of all the exciting things that I found. It feels great getting all those little irritating things out of the way now (e.g a good, bright torch (ok, that was £10); a bath mat, four dining plates). In an entirely less efficient/rational way, I've also been setting myself the personal goal of making sure everything is either:
1. beautiful
2. weird
3. Pure 1980s wonder
Everything clashes and is covered in a crazy pattern. Just the way I like it.