My advice, don't pay for the dealer to to the Autoglym protection, put simply they don't prep the surface properly before applying the product. Use a detailer and ask them to contact the dealership to go and detail the car before collection. They will spend the full day on it, clean it properly and apply better products. If you go for a ceramic sealant protection it will last at least 12 months. Not only that, it's probably cheaper than the £400 VW quote. Pro detailers often charge around £200-250 for a single day New Car Protection.
Depending on where you are, I might be able to recommend someone for the job?