Hi there.
I don't know about the High Street but I've come across this website:

http://www.cozumel-tours.com/biodegradable-sunscreen.htm

Also if you go onto Ebay and type in organic sun lotion this might help.
I hope this is of some use.
Best wishes.

David

I've been looking everywhere, can't see it in any shops in the UK

If you mean for the ecological parks, they either supply or sell (think sell) it there. I know we got some there (Xcaret) when we went but was a few years ago. If you need it for something else and can't get it anywhere else maybe go there first to buy some.??

They sell it & I bet its well over priced, so if I can buy some in the UK, I would rather do so.

Hi kim, its actually cheaper to buy it in mexico, at xcaret we had to buy some and it was around £9, the only biodegradable sun lotion I could find online is by the greenpeople and its £15.99.
I doubt you'd get it cheaper in the uk as more people buy it in mexico, you can get it in most shops over there too, shop around for the best price.
have a great time !

Thank you, thats nice (& unusual) to know.

Will buy it over there cheaper