Go on What Car and see what yours is worth...
Mine:
MG ZS Saloon 1.8 16v 120 4dr 2003 (53) 44,000 miles
Dealer £4,085
Private £4,015
Part exchange £3,945
Trade £3,785
A good bargaining tool for those who are selling as these seem to be high valuations!
http://www.whatcar.com/valuations