They can only say no.....I take it they haven't mis-priced and it's really worth 8k? If it's priced correctly for what it is and you've got cash, it's worth trying to get and extra £50 if you can
My friend went to see a horse that was up for £800 and iirc she only ended up paying £600 - go for it
Deffo try and get it down to a nice round figure, perhaps that's what they are hoping for, £550 is an odd sort of number....bit like cars, always stick a little on top to get knocked down
what ppl do here at fairs and the like, is the seller gives 50 back to the buyer for luck! try it and tell them its an irish tradition...they won't say no!