Now, the United Kingdom has concluded a materially identical administrative arrangement with the Council about the use of languages other than English recognized by United Kingdom law.
In practice, that means the use of the Welsh language which gets its status from the Welsh Language Act 1993 and the Government of Wales Act 1998. It also means the use of Gaelic which derives its official status from the Gaelic Language (Scotland) Act 2005. (On languages in the United Kingdom generally, see here).
Like the Spanish arrangement, the one with the United Kingdom provides that a person any may write to the Council - but indirectly - in any one of the languages recognised by law in the United Kingdom and receive a response in it. That person cannot write to the Council direct but must send the letter to a body designated by the United Kingdom government which body then translates it into English and sends it on to the Council. The Council responds in English, sends the response to the designated body which then translates it into one of the language of the addressee and sends it on. There are provisions in the arrangement also for oral debates in the Council to be in one of the languages recognized by United Kingdom law and for measures adopted by co-decision to be translate into them. The cost of all this is borne by the British government, not by the Council.