I was wondering if anyone knew any good places to buy this in the UK? I need to create a face mask for some scarring.

If its just for a one off scar on your face I would suggest going to a fancy dress or dance shop. They usually sell small jars of it.

or you can get it here
http://www.tiranti.co.uk/product.asp?Product=1288
Tirantis is my favourite, if you live in London you can just go there and buy a bottle as big as you need!
Or just order online, I don't know how much their post and packaging is.

Amazing, exactly what I wanted to know! I'll go buy the bottle. Cheers.

Some people are allergic to it though, so best to only get a little bottle or something first.

welcome, but as mentioned above do a skin allergy test before covering yourself. Just put a little patch of it on the inside of your elbow to see how your skin reacts.
I've personally never had a problem with covering myself in latex, but its best to be safe than sorry =]

Also, if you are wanting to do scars, it might be good to look into latex thickener. Its a thin white liquid which you only need a few drops of to make your latex thicker, you can sometimes get a consistency you can sculpt with while the latex is drying.
I recommend having a read about it online.

I'll make sure to test it, thank you for the heads up. I'll check into that thicker, could be VERY useful. Woah you are very helpful, thank you so very much.