In the British Army the 'correct' placement of miniature medals is either left lapel or left breast - depending on the type of mess dress worn. Those with lapels wear them there and extend onto the left breast if required.

The Royal Regiment of Scotland have put their dress regulations (with many a full colour picture) on the web for all to see:

http://www.army.mod.uk/documents/gen..._Rulations.pdf

The official mounting method for UK medals is swing mount, with few exceptions, but court mounted is more popular and accepted as the norm by most.