Thank-you very much for your replies: you've all asked about or highlighted the things I already think are issues.
I've been deliberately coy - it's not my house but PIL's, and the one that DP grew up in. Which might go some way to explaining his general defensiveness of it and refusal to consider any potential problems. It's been on the market for over 5 years now, virtually no viewing in the past year or so and no offers since 2011.
- I think that people see how long it's been on the market for on Rightmove/Property Bee and assume there's something wrong with it or that it would be impossible to sell on in the future
- I think it's over-priced, but because the bungalows in the area vary so much in terms of style/size/layout/plot it's difficult to make PILs acknowledge that this might be the case; they'll agree that it's at the top of its price range for size and location but insist that this is because it's much nicer than other houses which have sold for or are being marketed for less, or that their street is one of the most desirable in the already desirable area - I don't know Newton Mearns well enough to know whether this is really the case or no. I'd say they should be expecting offers around the £290 - £300 mark.
- I think that the bathroom and kitchen are dated and that prospective buyers are unwilling to pay top dollar knowing they would want to replace these. I also agree that the dining room is old-fashioned and that a lot of the decor is fussy and can be off-putting to younger people with more modern tastes. PILs refuse to alter this, and to be honest I don't blame them: after 5 years of altering their living space to try to please viewers with no luck, they must be sick of it.
- No garage or conservatory, no planning permission to add or extend (and no room either) and previous attempts to get permission for a garage have been repeatedly declined.
It's all coming to a head now because PILs have an interest-only mortgage, didn't make any arrangements for repaying the capital at the end of the term, and have now retired, making the ongoing interest payments unaffordable. They've asked DP and I if they can borrow money from us to cover the mortgage until it sells. However, bearing in mind the length of time it's been on the market and the lack of interest, before I start agreeing to lend/give them any of our money I want to have a frank conversation with them about the house and what action DP and I think they ought to taje to make it more saleable, including dropping the price if necessary, so that us making their payments for them doesn't go on for another 5 years.
So all points a big help, thanks 