In reply to Flinticus:
In my experience trade-ins fall into 2 categories
Cars which match the retail profile of the dealer - i.e. one which they can give a branded service and clean up and put straight onto their own forecourt with a price tag that gives them a worthwhile profit.
Anything else which goes to a trade auction. - in which case all they will offer is current auction price minus their costs.
If the dealer you are buying from sells second hand jazz for £1000 or more and has their own workshop - you may get a better price - otherwise every other dealer will only offer you auction value minus their costs - plus or minus how much profit there is in the car want to buy from them.
I think in your case - they are only going to be interested if you're buying a new car. Otherwise they just won't be bothered with the hassle of getting their regular auction broker to come and haul it away - they'll probably give you a story about how they'll can only offer you peanuts and that you'll get a better price selling it yourself.
Post edited at 07:58