Ask for the mount to be replaced with the cambelt and see what happens?
It is illegal under the Road Traffic Act for both business and private individuals to sell a car that isn't roadworthy for which you have at least two items to question:
1. Failed engine mount/Temp fix admitted by garage work was undertaken by....is the garage in question happy to let a car onto public roads with temporary fixes?
2. Decat.
There is potentially £4k's worth of repairs at stake here but you will probably be pursuing with your own money/time and resources.
Where was the car advertised?
You have to treat many private sales with caution as so many people will claim to have a genuine reason for sale but might be hiding problems that they don't want to repair.
Thanks for all of the replies. You're right it's probably the only protection a buyer has in a private sale, the car must be roadworthy in that it cannot have any fault with a) The brakes b) The Steering c) The structure of the car.
Having been to see both Citizens Advice and a Solicitor over the last few days I'm looking at 'C' as the mount is integral to the structure of the car. The question over the MOT can be raised with Trading Standards and the police could be involved as the seller has technically obtained money by deception. None of the issues were declared at the time of sale.
The worrying thing is the safety element, if its a dodgy head, cambelt issue, I would have been prepared for it but to sell a car that could potential kill is something else.
I prepared a letter before my visit to the solicitor today and luckily covered everything so manage to get away with a free consultation. Must now wait seven days for a reply, which in itself is a nightmare as no one can touch the car, so I have no idea of the state of the rest of the engine or whether it is salvageable, if the seller refuses a refund after the seven days and it is repairable I can authorise the work and will then chase the costs in small claims court.
I've had it at an 'independent VW garage' and now at a main dealer (just to cover all angles and get two opinions/quotes) and everyone keeps telling me what a great car it is... it just happens to have one of, if not the most expensive rectifiable faults they've seen!
Thanks again for your help, I'll let you know what happens...