Where France stands
France is inside the Hague Apostille Convention, which means a single British certificate is accepted there without anything added to it. That agreement is doing all the work. It was settled between governments, so it does not vary with the kind of paper you hold, the office that issued it, or the reason you are sending it. An apostille for France is therefore the complete answer rather than the first move in a longer sequence.
The desk that is not there
On many corridors a consular desk adds a final mark, and readers arrive expecting to find one here. There is none. No consulate needs to see the sheet, no second fee falls due, and no second queue affects your date. This matters most for planning: people budget a fortnight for a stage that does not exist and then treat the finished file as unfinished. Document legalisation for France ends when the certificate is attached.
The shortcut that is not there either
The mistake also runs the other way. Some readers have heard that certain papers now cross between European countries with no mark at all, and assume that covers them. No such exemption applies on this route, so the certificate is still required. An apostille issued in Southampton for use in France remains the thing that makes the paper usable, and skipping it on the strength of half-remembered advice is the most expensive way to save a fee.
What is left once both are removed
Strip out the stage that is not there and the shortcut that is not there, and what remains is one office, one charge and one round of post. An apostille from United Kingdom to France is issued by the FCDO Legalisation Office, which handles every British case from a single address and never opens a counter. Anyone reading up on what you need for an apostille for France is really reading a very short list: the right document, the fee, and a safe return address.