Restoring faded red paint?

yes most people make the mistake and do not seal after cutting. but you are on the right track cut /polish/ then resin to seal it all in. its the UV light that bleaches the red paint so unless you want to put factor 40 on the bonnet evry 2 hours the autoglym should be ok.

I've just restored an '85 red roof that had faded, using T-Cut and a lot of elbow grease with some equally old wax to finish. It looks like (nearly) new. I don't think the wax type matters too much, it's the cutting and hard work that does the trick.

. its the UV

Is it true that sun cream on car windows reacts and leaves a milky colour?

I polished a red K reg Ford Orion with the Autoglym paint restorer. It's got some sort of wax or similar in it, so you can't wash it off, so you have to keep polishing until you've got it all off. Then you get the super resin polish out, use that, and then wax it, which will keep it looking good for longer. I'm assuming it's not clearcoat paint if polishing has worked before.

Farecla G3 and G10 would be a lot easier. Would cost you about £15 for a tub of G3 and bottle of G10 at an auto / paint factors, and both compounds can be washed off and thinned out with plain water. You can then wax it with Autogylms resin polish and wax.

All clear for polishing then. I know some cars around that age had clearcoat, but AFAIK it's mainly things like Merc / BMW / Jag. You'll be alright with the Autoglym if it's not too bad, the car I did took a lot of polishing (11 years of only ever being cleaned with cheapo wash and wax, and never garaged), the bonnet and roof were like pink chalk so it was a swine to do (best part of a day to do the paint restorer and resin IIRC). If it's that bad, go and get some G3, I found it difficult to get a decent finish using Autoglym, I had streaks of paint more polished than the others. Of course, you can fix all that with more polishing :P.