In reply to LastBoyScout:
> they probably only cost me about £45 at the time
Would I be right in thinking, based on that cost, that they aren't prescription lenses?
If it would be of any interest to you, I have a pair of Julbo Nomad 125 Zebra (i.e. photochromic from cat 2 to cat 4) sunglasses which I can't use any more due to my deteriorating eyesight and which I have been planning to unload via a certain well-known auction site. I used them for skiing very happily for many years before I was forced to switch to prescription varifocals (these days I use OTG goggles with a photochromic lens). The style may not be the same as your current ones though, see here: https://www.polarsport.pl/media/catalog/product/cache/d6e45dfc1b25b95a4e830...
They're in the original Julbo case, with the originally supplied choice of black or silver glare shields (as per the photo linked above). If you don't like the glare shields you can leave them off.
Drop me an e-mail via UKC if you would be interested and I can give you more details.