Hi there
Ok this is only my opinion, but supaguard is not a product I'd choose, in fact I find it rather poor. I have had many new cars, all with £300+ options such as Lifeshine, Diamondbrite and Supaguard, all fail miserably compared with proper detailing, regularily applied products.
Id recommend Meguairs, Zymol (depending on budget) and Zaino. You will find the results a lot easier and far better compared to AG.
In my experiance!
HTH 
ive used silver seal on my customers cars for years now with no problems at all!!!!! alot of people think that once they've had these treatments applyed to the car they dont need to seal it or wax it anymore,resulting in the product failing so to speak,these products are very good if backed up with regular sealing on top and regular waxing.
im possibly missing something here but whats the difference between paying £200+ for your product then having to top up every 2 months or so, or not buying your product applying a £10 product to start with and toping up 2 months later with a normal wax ?? ?
anyway i would never ever have any of these premium priced dealer preps (diamondbrite, silverseal, etc etc ) near my car, and i especially would not let them apply it
