Basic premise is everything is negotiable.
As a a general rule new listings will be less inclined to negotiate and listings that have been around for a while will be more inclined to talk turkey. Most sellers think accessories add value to the car when in reality they should not BUT clearly if you take that approach the seller will not sell but something to take into account.
Two basic approaches - make a silly offer first and see what happened - as long as you are getting on with the seller you both can have a laugh and then get on to serious bargaining. Second offer 10% less than you would reasonably be prepared to pay and see what happens - if rejected this gives you a 10% buffer to negotiate further.
Good luck with it.
Garry

