The longer road, and why it is not used here
British paper reaches a foreign desk by one of two roads. The long road is a chain of stamps that finishes at a foreign mission abroad. The short road is a single slip that Convention countries read on sight, with nothing following it. Australia takes the short road, so document legalisation for Australia stops at the British stage and no mission joins in at all.
Inside the Convention since 1995
Australia joined the Hague Apostille Convention in 1995. Since then a British sheet carrying the slip is read there on its own terms: an apostille from United Kingdom to Australia needs no second stamp and no appointment at a consulate. The whole chain runs inside Britain, which is unusual enough that people often wait for a step that never comes.
Where the paper starts in Derby
Derby Register Office at Riverside Chambers, Full Street, Derby DE1 3AF holds the entries behind local civil records and can issue a fresh certified copy, which is the sheet worth putting in the post. The FCDO Legalisation Office, PO Box 6255, Milton Keynes MK10 1XX, adds the mark and posts the bundle back. An apostille issued in Derby for use in Australia is read straight off that returned slip.
A price you can total in advance
Because only one office charges, the arithmetic is short: £45 per document by standard post, or £40 per document next-day for registered businesses, multiplied by the number of sheets. Nothing else on the stamping side is billed to you. Where the calendar is concerned, the waiting is postal waiting at both ends, so the count of days rises with the size of the pile rather than with distance.
What the slip does not decide
The mark stands behind a signature. It does not say your record is current, complete, or the right one for the purpose someone in Australia has in mind. On a two-stage route a second desk sometimes notices a mismatch; here there is no second desk, so a wrong choice travels all the way to its destination unchallenged. Read the request you were sent word by word and pin it to a named paper first.