So I bought my 2.7TDI A6 Avant brand new in 2005 and have been driving it ever since. It is coming up to 20 years old and 200,000 miles but is well loved. The engine and body work are in good condition and it has been looked after - it's a great tidy car.

A couple of month ago I went to fill it up with fuel and on getting in it to leave the forecourt, the car starter wouldn't even turn over - completely bricked. The message on the screen said to remove the pressure on the steering wheel. The steering lock was engaged but the ground was flat. The RAC came out and couldn't do any with it. Eventually they had to lift it and drop it at a garage. My usual garage couldn't take it so it was taken to a garage recommended by the RAC mechanic.

The garage that has it have had to change one of the brains (I think they found a second hand brain somewhere). The car apparently now starts. However, the MMI is no longer coded to work with the new brain so does not work. A new MMI is expensive, so they have been looking for a used MMI and somehow need to remap it for this car using some specialist. They are having trouble with this and the car has just been sitting there for weeks. Tax, MoT and insurance etc are all due soon.

Big diesels don't have much value these days - even in good condition. I'm already up to around £700 of costs so what do I do next? Spend more on new MMI kit and specialists, collect the car and try fixing it elsewhere, give up and sell it?

Any useful thoughts appreciated - thanks.