I'd offer a small bit of advice;
As a motor trader I have no qualms with taking a p/x. However, I will always try and be fair and offer a reasonable price. However, I would offer less than I could get the vehicle from auction. So, if I need to dispose of the vehicle I can send it to auction and not lose out.
I would suggest entering the vehicle into auction yourself. You will get more than a p/x offer typically. You will have to pay to enter it, with fees etc...but it can work out well for you.
Auction doesn't mean cheap always. If you have a room full of 100 plus people all trying to make a living they will all consider the vehicle coming in and sometimes things cna get interesting. If I go to auction for a particular vehicle, I will come away with it no matter what. On a 2003 3.2 Elite with low miles I will always get it, out bidding anyone else, even over £3000 because I know what I can do with the vehicle.
I would suggest you don't try and sell though British Car Auctions (BCA) They are excellent, but not geared for the private seller. Try a local auction first, if in doubt anyone can give me a call and I'll see what I can do.
Remember, it's still your car, £250 is a stupidly low offer even considering profit margins and all other things people don't think about.