Its difficult for anyone to give their opinion as we dont know the full story but usually I would say its worth a lick of paint at least. I recently bought a house that had been on the market for over 2 years and the decorating in some rooms was hideous but I was prepared to look beyond it at the plain 4 walls. I guarantee that had the walls been painted white or cream and a neutral colour carpet the house would have sold within weeks.
Doesnt need to be that good a job so if you know a half decent decorator who can get it turned around in a few days then I would imagine your looking at no more than £500 including the paint.
A friend purchased a giant mansion at a ridiculously cheap price, like 100-150K under value really (paid 300K while everything on the block of similar size is 400-450K. The thing is very new (2007 build), very high quality high end house in an expensive neighborhood, granite tops, marble bathrooms, hardwood floors and cabinets.
But the decor was h most horrific experience you have eveyr seen. Like bright neon yellow paint in the living room, barbie pink dinning room, black and yellow bee stripes in the master bedroom, 1930s flower wall paper in the kitchen, polka dots in the bathroom, hideous hand painted muriels on the walls done by someone who cant paint at all. Weird assortment of furniture form pseudo antique, to art-deco, to cheap ikea tat. Nasyt rugs throughout.
People looking in that area have the money and people that kind of cash don't want to buy a house where every room will have to be redecorated. It was so disgusting it was impossible for most people to see beyond the putrid colors.
The thing was apart from the walls (and the furniture/rug/art that would be removed) the only thing needed was a top to bottom paint job. The kitchen was superb with black granite counter, hardwood cherry cabinets, stainless steel fridge, 6 burner stove, double oven, hardwood floors. Even the carpets were fine, standard beige affair put in by the builder, they were just hidden under vile rugs.
A few days after purchase a few of us went in and paint every room in a neutral base paint. Te house already looked great. they then spent the following weekends slowing painting in room and the house looks a million dollars TBH.