Thanks for prompt and clear reply. It's a product supplied and a applied by Halfords to keep window clear.

The "Roadsmart" magazine which came today includes an ad for "Liquid Glass" which claims to reduce dirt build up, beads water (as Rain-X does) but also claims it protects from stone chips and can be used to protect alloy wheels.

You can buy stuff like that to protect the screen of a smartphone or tablet, I've used it myself in the past. It was applied using a thing like a 'wet wipe' impregnated with the product, just wipe the screen and leave it to dry.

Not sure I'd be keen to use it on a car windscreen without hearing the experience of others who'd used it though.

Rain X works well on side windows - the droplets blow away.

I'd be much more cautious about using it on an area swept by a wiper where, after a short period, it tends to smear.

As above, fine on side windows but I found it an absolute nightmare on the windscreen when I tried it some years ago. Far better to have good wiperblades and degrease the windscreen often using some IPA or ethanol.

Indian Pale Ale?

More likely Isopropyl Alcohol