This article looks interesting - on the various legions in British service - in particular German, Italian and Swiss. The National Archives say
The Enlistment of Foreigners Act 1854 allowed the government to recruit foreign mercenary troops to make up the low number of British men being recruited during the Crimean War. These mercenaries formed the British German, British Swiss and British Italian Legions, often collectively called the British Foreign Legion. Recruitment began at the beginning of 1855, and eventually 14,000 men joined the legions. None of these men saw active service, although a number of regiments had arrived in Turkey when peace was signed. At the end of the War the Legions were disbanded. Men were encouraged to emigrate to the colonies and many from the British German Legion went to Cape Colony.