I have been asked several times this week about the 'special key which allows access to WC's' - so I thought I would share the answer!
The special key is commonly known as a Radar key. It enables access to nine thousand toilets - these are in all sorts of venues - shopping centres, department stores, transport links such as bus and train stations and a variety of eateries such as pubs and cafe's.
The key is available via: http://www.radar-shop.org.uk or via 020 7566 0122. The key has a current (Dec 2012) price of £2.25 with £1.75 postage and packing.
To help locate the WC's when out and about they also offer an i-phone app from the App Store. This has a current cost of £4.99. Alternatively they offer a National Key Scheme guide which lists the locations of all the accessible toilets. The current price for this is £8.50.