They are surfacing at airports too in an attempt to cut down on the number of plastic bottles used and are being installed through the generosity of the water industry.
I've also used one at Gatwick South terminal, upstairs between the Granary Store and World Duty Free. You can also refill an empty bottle in any catering outlet.
Are there water fountains after security?
Yes, we have water fountains available after security in both terminals and all our restaurants and bars will fill bottles for free.
There are probably others. It's ridiculous how much some airports charge for a bottle of water. At WH Smith it is cheaper to buy a Daily Telegraph which comes with a free bottle of water! You can then throw away the newspaper (in the recycling bin of course).