If you are in the Marshall Islands and in need of consulate assistance then you will need to contact the British High commission in Fiji as there is no British Embassy in the Marshall Islands. The details are listed below with other more common information which people are searching for.
The High Commission cannot provide you with a new passport but can provide you with an emergency travel document. If you need to here how to do this.then this needs to be done online. You can see
The British High Commission does not do birth registrations any longer. You will now have to do this yourself by post. See the writing on British Born Abroad on how to born abroad.