The problem with AutoGlym is not the product itself! (I'm assuming you're talking about dealer applied Lifeshine kit). The product is actually 'OK' (not the best but not as bad as some people make out).
The problem is that the dealer employed valeters either a) don't get the correct training in the application of the product or b) don't get an adequate time to apply it. I'd be inclined to say that it's a combination of the two!
With sealants systems like LifeShine, Supaguard, Gtechniq, CQuartz and many others, it's incredibly important to clean and prepare the surface to allow the sealant to bond properly. Once it's bonded, most need 8-10 hours dry curing time before they are fully effective. I'd hazard a guess that the dealer valeters don't spend more than 1 hour per car prepping it for collection, never mind the 6-8 (sometimes many more) hours it takes to apply the system correctly. That's not their fault, or the product's fault, its the fact that dealers don't have the time or budget to allow valeters to spend a full day prepping a car! (fully understandable from a financial point of view)
The issue of the price... £400 is ridiculous. You could get a professional detailer to spend a full day prepping the car with results 20 x better for £200-250 without doubt. The difference would be immeasurable!
I would be buying separate products which do a much better job and it would cost < £200
Hope this helps!
Jon