The word you were handed
Most people arrive here holding an instruction rather than a plan. An employer, a college or a bank abroad has asked for an official, stamped version of a paper, and the word used for it was borrowed from somewhere else. The wording of that request does not pick the road. The country at the far end picks it, and for the United Arab Emirates the road runs past a consular desk before anyone will read the sheet.
Where the United Arab Emirates stands
The United Arab Emirates has not joined the Hague Apostille Convention, so the short single-mark route does not exist on this corridor. There is no apostille issued in Southampton for use in United Arab Emirates, and none from anywhere else in Britain either. What the request really points at is document legalisation for United Arab Emirates: certification by the FCDO Legalisation Office first, then a stamp from the destination's own consular desk. Two marks, in that order, on one sheet.
What to tell the person waiting
Reply with what this road actually produces, not with the word you were given. An apostille from United Kingdom to United Arab Emirates will not close the file, whatever it cost, so promising one only pushes the real answer back a fortnight. Say instead that the paper is going through a British certification and then a consular stamp, and give a rough order of events. That is the ordinary route for papers leaving Britain for this destination, and it is what the finished sheet will show.
What carries a price, and what does not
Only the British stage has a published charge: £45 / document by standard post, or £40 / document next-day where a registered business is sending it. That falls on each sheet, so three records cost three times over. The consular stage adds a charge of its own and a wait of its own, both set by the desk that gives the mark. Anyone reading up on what you need for an apostille for United Arab Emirates lands in the same place — the destination fixes the road, and the paper you hold does not.