Notary, then apostille and consulate.
The FCO has two offices. The one open to the public is at Milton Keynes, which is accessible by train from London. It is 55 miles/ 85 kilometres away. They charge £30.00 per document. Documents need normally to be signed by a notary before going to either FCO office.
The other FCO office is at Centre Point in London and is open to notaries and some other businesses. They charge £75 per document. The general public cannot go there, but notaries can take documents there on behalf of clients needing a swifter service.