Update on the Autoglym roof treatment now it's been on there a few weeks.
In summary: I won't be using it again. The cleaner made no noticeable difference - to be fair I had scrubbed it with Milton solution recently, but I was hoping for some kind of positive change.
My biggest gripe is the treatment. It does indeed bead water all over the roof - it then looks ridiculous until the beads fall off or the roof properly dry out. Worse, because the water is just sitting on the roof, I have noticed water dripping into the car when opening and closing the roof as it just runs off and splashes.
Compare to pre treatment (or other brands that do *not* repel water), a soaked in wet roof looks nice and black and doesn't drip into the car.
Total rubbish
Also had the M wheel airbag off today. For some reason the horn was not working if the right hand side of the airbag was pushed (left and bottom fine). For some reason the 'C' shaped clicky springy bit inside was not giving a metallic click sound when pressed on the right, despite making clear metal contact. Didn't investigate, just swapped the part from my original wheel and now working fine.