Where Ghana stands
Ghana has not joined the Hague Apostille Convention, so a lone British mark does not answer for a paper used there. Papers going that way need embassy or consular legalisation, which in practice means document legalisation for Ghana runs through two desks: the FCDO Legalisation Office certifies the British sheet, and a consular desk acting for Ghana then adds the mark its own government reads. There is no apostille issued in Southampton for use in Ghana that removes the second step.
The sheet that does the travelling
Two desks means two journeys, two sets of hands and a longer spell when the paper is somewhere other than your house. That is why the copy you commit deserves a moment's thought. Where a public register holds the record, Southampton Register Office issues certified copies from the entry itself, so a new one carries the same content as the version you already keep. The register does not part with anything by making a copy, and neither do you.
Paper nobody will make again
The harder cases are the ones with no register behind them: a diploma, a signed board resolution, a letter of employment. Whether a second copy can be had at all depends on the body that issued the first, and some will not repeat the exercise. Settling that question before the envelope leaves is worth more than any speed you might buy later, because the risk on this road is not delay but a sheet that cannot be replaced at any price.
What each stage costs you
The British stage publishes its price at £45 / document by standard post, or £40 / document next-day for registered businesses, and it falls on every sheet you put through. The consular stage carries its own charge, set by the desk that gives the mark. An apostille from United Kingdom to Ghana is not a purchase that shortens either half, and anyone reading up on what you need for an apostille for Ghana will meet the same two desks in the same order.