Apostille vs. Embassy legalisation for Cambodia
Cambodia has not joined the Hague Apostille Convention, so a single British certificate does not settle a paper used there. Documents bound that way need embassy or consular legalisation instead, which is a chain of acts rather than one act. No apostille issued in Glasgow for use in Cambodia stands as a finished file, and the consular desk supplies the closing mark.
Cambodia's Hague status & what it means
Sitting outside that treaty means the finished article has layers, and each layer names the one beneath it. That is exactly why the far end is the right place to start thinking. The shape of what somebody must finally hold decides the shape of everything upstream, right down to which sheet is printed on the first morning.
The Glasgow → Cambodia route, read in reverse
Read forwards, the route looks like an errand list. Read backwards, it looks like a series of constraints. The consular desk needs a British-marked sheet. The British office needs a signed and sealed paper it can speak for. The register office needs to know which entry you mean and how many prints you want. Each need is set by the step after it.
Two government offices do that British work, and neither of them is ours. Glasgow Registration Office at 45 John Street, Glasgow G1 1JE prints certified extracts of Scottish civil entries. The FCDO Legalisation Office at PO Box 6255, Milton Keynes MK10 1XX works by post and returns the file to the sender, so nothing is collected in person.
Cost & timing for this route
The British charge is £45 / document by standard post, or £40 / document next-day for a registered business, and it is counted per document rather than per envelope. An official charge follows at the consular stage. Since an apostille from United Kingdom to Cambodia is only the first of two paid acts, a wrong choice at the start is charged twice over.
The decisions that belong at the start
Name the record, name the person, count the sets, and set a start date rather than a finish date. Then let the route run in its own direction without revisiting any of those four. Everything downstream is other people's work on other people's clocks, and the only part you truly author is the brief you write on day one.