Three purchases, not one bill
It helps to stop thinking of this as a single service with a price. You buy a certified copy from a register, then a check on the signature that copy carries, then a consular stamp on top of the result. Different bodies, different charges, different moments — and only the middle one has a published figure you can quote back.
What you need for an apostille for Republic of the Congo is therefore a budget with three lines in it. The middle line is fixed at £45 per document by standard post, or £40 per document on the next-day service open to registered businesses. The other two vary with the office and the paper.
What each fee actually delivers
The register office fee buys a sheet that counts as the record. That is why the certificate you keep at home never has to travel: a certified copy stands in for it completely, and a mishap in the post costs a fee rather than something irreplaceable. Coventry Register Office prints these from the entries registered in the city.
The Legalisation Office fee buys one comparison and one attached certificate. An apostille issued in Coventry for use in Republic of the Congo is not produced over a counter anywhere, because that office works by post for the whole country. The consular fee buys the final mark, and document legalisation for Republic of the Congo is only complete once it is on.
The thing that is not on sale
None of these fees buys acceptance. Every desk in the chain vouches for the step in front of it — this copy matches the entry, this signature matches the specimen, this certificate came from that office — and none of them speaks for the body that will finally read the file. Paying more does not change that, because there is no premium version of a signature check.
This matters when a deadline is close and the temptation is to spend your way out. The spending available to you is the next-day option at the British stage. Everything else on this route is waiting, and an apostille from United Kingdom to Republic of the Congo would still leave the consular stamp to buy afterwards.
Where the savings genuinely are
The real economy is getting it right first time. A sheet that has to be replaced is charged again at every desk, so five minutes reading the names, dates and places on a fresh copy is worth more than any discount. So is deciding the count of sheets before you order, since extra copies printed together cost one visit rather than one whole route.
Beyond that, treat the certified copy as the cheap, replaceable part of the exercise and the finished sheet as the expensive one. Coventry Register Office, Cheylesmore Manor House, Manor House Drive, Coventry CV1 2ND, can print another copy of a civil entry; nobody can print another finished file once the stamps are on.