Im in the same situation at present with both selling my present car and looking at a new one. People are contacting me asking what is the lowest you will go. I've basically said, its been reduced and im open to discuss all genuine offers, as there is always room to do a deal, got my mk4 anniversary pd up for £6,795 now, still getting day dreamers and time wasters.
Only thing i could say is be honest and upfront with the seller, you like the look of the car, this is your budget.... see what they say, they will appreciate you being honest and upfront, rather than waste there time.
Try and look for things to bargain with, service, tax, MOT, cambelt etc.. all can be used to negotiate. The car im looking at 07 edition 30 dsg, is due s service & cambelt, so have prices from VW to be used to haggle, either the garage will get them done or i factor it in to the price.
Good Luck