I have just had a couple of 16a sockets put in my garage. There are 2 types of plug/socket. 1 with a screw ring for securing the plug and the other the normal caravan type.
I used these sockets
http://cpc.farnell.com/PL09010/cabl....us0?sku=pro-power-sq1663ca&_requestid=646671
The screw ring ones are rated IP65 (I think but it could be 45) and are rated for use in damp areas. These would not be standard 16 amp sockets.