There have only been two main types of plug used continuously in the UK, the BS546 and the BS1363, there have been some regional variations and whatnot, but they ended up standardising on the 546 or 1363 plug & socket...
The BS 546 had I think 5 main plug types since it's inception, the 2 pin 2A and 5A plugs, and the 2A, 5A and 15A plugs (I think there may have also been a 30A plug, but that was for industrial use only), after that, it was 13A BS1363 only, with the 3A, 5A and 13A fuses inside the plugs...
A lot of places that were colonised by the British empire (China, Africa, India, and some other places I can't be bothered to remember) also standardised on one of the two types, South Africa is a good example as they still use the 15A plug as standard, whereas here in the UK the 15A plug is usually used in theatre lighting rigs
See Types D, G and M here:
http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets