Interesting responses guys.
I've tried the 3M kit (twice) with little benefit - actually I thought the first attempt was a waste of money. I put it down mainly to my technique and the fact that I just couldn't get on with the circular pad on the drill - in terms of having proper control.
I bought the Quixx kit on a whim, the last time we were in The Range. At £12, it's cheaper than the 3M kit and includes all the relevant grit pads, along with the polish (and importantly) the sealant, for afterwards.
https://www.therange.co.uk/motoring/vehicle-maintenance/quixx-headlight-restoration-kit/#935141
Just tried it on the 182 now and the results pissed all over the 3M offering. Granted, with headlights facing the full amount of crap thrown up over 12+ years and 140k+ miles, they will never be 100% flawless. But the result is much better than the previous offering - to an extent that I might even buy another one of their kits later in the year.
Definitely recommended.