I'd certainly be getting them to take that off. They are trying it on. Most people that don't 'know' cars will say "it's only an extra £15 a month" and believe that these products do all that the blurb says the do. As others have said, a pro detailer will do a much better job with first class products for much less, or you could do it yourself if that's your thing.
I often wonder how many people who fall for the sales patter actually get the products applied. I know a valleter at Vauxhall dealership that is given 1 hour to prep a new car, including applying Guard X. It just can't be done, so the salesmans attitude is"fcuk it, they'll never know."