If you are visiting Yemen then speak to the staff at the British Embassy in Yemen. They will be able to provide you with consular assistance and also allow you to register your marriage in Yemen at the embassy, register a British national born aboard or even register a death.
You can also speak to them about a Notary Public if you need to have documents signed. If you wish to pay a visit to the UK either as a tourist or as a partner of a British national then you can apply at the embassy in Yemen for a British visa. Note that the Embassy is close to the Mövenpick Hotel in Sana’a Yemen and it is closed on a Friday.
British Embassy Sana’a, Yemen
British Embassy 938 Thahr Himyar Street PO Box 1287 East Ring Road, near Mövenpick Hotel Yemen