We moved back from France to the UK in May and dad wasn't sure what to do with the car. He has decided to leave it at the airport in France, but this means we now need a UK reg one. Are there any sites you can find people selling their cars direct as apposed to garage dealers?

Britain is awash with second hand cars and one of the cheapest places in Western Europe to buy. Much cheaper than France for substantially the same thing. For example
Find used cars for sale on Auto Trader UK

Gumtree is another option.