What do you think a Focus RS with one lady owner, 21k miles FSH, couple of shiny bits and tinted windows etc is worth?

A fiend of mine is selling hers but didn't get much interest at £16k, she was offered £14k by a dealer who 'wanted it for his own car' but I think that's far too low. What's the going rate for a good one?

Cheers,
Iain