Apostille vs. Embassy legalisation for Chad
It is tempting to read a long route as a complicated one, and the two have almost nothing to do with each other. Whether a paper finishes with a single certificate or carries on to a foreign desk depends on a treaty, and a treaty has no sense of geography at all. Document legalisation for Chad involves a second desk for that reason and for no other.
Chad's Hague status & what it means
Chad has not joined the Hague Apostille Convention. An apostille issued in Derby for use in Chad is therefore never the finished article on its own, however carefully the file is put together and however quickly it gets there. Treat an apostille from United Kingdom to Chad as the opening mark, with a consular stamp to follow, and the timetable you build will match the one the route actually runs on.
The Derby → Chad route step by step
The first half is the ordinary British one. Derby Register Office at Riverside Chambers, Full Street, Derby DE1 3AF supplies certified copies of local civil entries, so the version at home need not move. The FCDO Legalisation Office, PO Box 6255, Milton Keynes MK10 1XX, then adds its mark through the post. Everything up to that point would read the same on a page about a country twice as far away that happens to be inside the Convention.
Cost & timing for this route
British prices are published: £45 a document by standard post, or £40 a document next-day where the sender is a registered business. Notice that neither figure varies with the destination, which is the clearest sign that distance is not what the British side is pricing. The second stage carries an official charge of its own that this page does not quote, so build the budget as one known half and one open half.
Destination-specific requirements
Planning around miles produces the wrong shape of plan. It puts effort into couriers and flights, when the part that lengthens this errand is a desk with its own rules, its own hours and its own view of the file. So what you need for an apostille for Chad is room in the calendar after the British mark, plus the sense to keep the record itself in good order, since the second desk sees the same sheet the first one saw.