The road with a fourth party, and the road without
Some destinations pull a foreign desk into the job: the British mark goes on first, then a consular stamp on top, and the file is finished only abroad. Spain takes the other road, where a single slip is read on sight. So document legalisation for Spain has no consular chapter, and the cast of the errand shrinks by one.
Inside the Convention since 1978
Spain joined the Hague Apostille Convention in 1978, and the effect on your planning is direct. An apostille from United Kingdom to Spain is read there without a further mark, without an appointment and without a second official charge. The whole chain sits inside Britain, which is why the errand can be described from beginning to end on one page.
The two offices on the list
Derby Register Office at Riverside Chambers, Full Street, Derby DE1 3AF supplies the sheet when the paper is a local civil record. The FCDO Legalisation Office, PO Box 6255, Milton Keynes MK10 1XX, supplies the mark. An apostille issued in Derby for use in Spain is the product of those two steps and nothing else, both done through the post rather than at a counter.
One charge, counted per sheet
The published rates are £45 per document by standard post and £40 per document next-day where the sender is a registered business. Because the unit is the document, two records in one envelope are billed twice. The calendar is set by postal legs at both ends, so the honest question is how many sheets are going, not how far away the destination is.
Why naming everyone helps
Most of the confusion on routes like this comes from advice written for somewhere else, where a consulate really does have a part to play. If a set of instructions mentions a party who is not on your list, the instructions belong to a different destination. Holding the short list in mind lets you spot that immediately and ignore the extra step.