Sounds like you got free Lifeshine or Supagard from your dealership. That's a gift for themselves - usually retailing for about £300, you get about £20 of sealant, fast glass and scotch gard-like product for the seats. They'll have built in that product to your discount as if you'd purchased it - the sales-person personally gets about £60 commission for every "sale" of it, likely marginally more than commission on the car itself.
I definitely wouldn't buy it, but if its free and applied properly, your car's bodywork will bead up in the wet for 8-12 months before you'll need a top up.
