I really need to clean the Lenses more often. It's been over a year anyway... Possibly a lot longer I think.
I didn't even clean them for the NCT (as you can see in the photo I posted over in the NCT forum).
I cleaned them the other night though (clocks going back and all), and wow, such a difference. I reckon my lights will be much more effective at night now with less light been obstructed by the fog/cloudiness.
Had tried using Simoniz compound which is like a hard wax type, and I'd also tried using Liquid T-Cut, but the best I used was the Formula 1 liquid compound. It's more like a paste than a liquid though. It doesn't run. Anyway, delighted with the old results.