The language Belgium asks for
Belgium reads this file in French, so French is what your paper is turned into. A certified translation into French in Sheffield is written from a scan, and the English document itself is never altered. The French pages are an addition to it. They arrive signed and dated by a translator who is answerable for every line, because Belgium treats the text as a record and not as a rough guide.
An address is a route, not a phrase
Half of an official page is not really language at all. It is a set of pointers: a house number, a street, a postcode, a reference to a place. Those pointers only work if they still match the paper they came from, so they are carried into the French text exactly as printed, and explained in French around the edges rather than inside them.
It matters most when two sheets have to be matched by someone who reads no English. A reader in Belgium runs an eye down the French page, finds S1 2HH, and finds the same string on the English sheet. The pointer did its job. Had it been rendered as a French-sounding phrase, the two pages would look like records of two different places.
Names of places and offices
The same rule covers Sheffield, South Yorkshire and the name of any body printed on the paper. None of them is translated, because a name is a label for one thing in the world and a translated label points at nothing. What the French text adds is a short description: this office keeps the civil register, that one holds the court file, this line is a county rather than a town.
That small habit prevents the most common muddle on this route. A Belgian reader who meets an unfamiliar English name with no gloss has to guess whether it is a person, a town or a government body. Two words of French remove the guess, and the guessing is what turns a straightforward file into a question you have to answer twice.
What it costs and how long it takes
Pricing is £25 a page, so the size of the job is known before any French is written. Standard work runs 2–4 business days from the moment a readable scan lands, and there is an express route at 24–48 hours for people working to a fixed date. Both produce the same signed set; the faster one simply buys the translator's diary rather than a different product.