I never negotiated in England so I'm lost on that issue. But go over your weights and dimensions to make sure truck and 5er are good matches for each other. Understand what hitch would work best. RV salesmen here across the pond will try to convince you of anything that facilitates a sale. So know what you are buying. Salesmen here will negotiate with you on both price and equipment. Make sure the dealer will be spending significant time with you showing you comprehensively the operation of your new purchase.