Superdrug are now doing their own brand freeze treatment for warts and verrucas - like Wartner or the Scholl sprays. £6.99 is a very good price on its own. Get a further 25% off if you can be bothered to buy something else (paracetamol for 14p is good), fill in the questionnaire online and get the 25% off discount code.
Not yet online, but I have seen instore in Bristol Bedminster.
The image is Wartner - can't find a pic of the Superdrug box.