A good car which despite its size can be run quite reasonably if you use non franchised Renault experts.
I have had to spend very little on the car since buying it and it has been very reliable. What you get for your money is very impressive. However the one previous owner spent a lot of money maintaining it with the main dealer and before selling the car spent £800 after the head gasket went. I was surprised that this happened and later learnt from my local garage that this is a common fault on the multivalve engine and they have known it to happen at lower mileges. If I had known this before it would probably of scared me off from buying one.
The digital dash is also a cause for concern. They do go wrong and if it fails you lose the milometer and fuel gauge amongst other things. I am told Renault do not repair them but do an exchage for £1000+. This is probably how much my car is worth so I hope it never happens. However it's a nice car to drive and passengers appreciate its comfort. There are a number of models that do not have the digital dash or the multivalve engine.
I believe the normal 8 valve motor is very strong. I had one in my Renault 21 which burnt no oil having covered 155,000 miles before I sold it. My advice if you want a Renault 25 is to find the best example you can with a service history, don't pay to much as these cars are not easy sellers and avoid the auto gearbox.