The sheet decides the result
Nothing is filled in from memory. Every name, date and seal in the new text is read off the copy you supply, so the state of that copy sets the state of the result. A worn fold through a middle line, or an image that clips the bottom edge, leaves a hole that only a better picture of the same sheet can fill.
A clean copy of a civil record
Birth, marriage and death entries never have to be put at risk. Fresh certified copies are drawn from the register itself at Leeds Register Office, 2 Great George Street, Leeds LS2 8BA, and one of those can stand in for the sheet you keep at home. A new copy is flat, unfolded and easy to read, which is what a certified translation into Nepali in Leeds needs to begin from.
What the statement records
The signed sheet names the document, the language it was turned into, and the day the work was done. That is why a certified translation for Nepal cannot quietly be moved onto a different piece of paper afterwards: the statement points at one copy, and any reader can hold the two side by side and see whether it does.
Cost and clock
The rate is about £25 a page, counted by sides as they were issued. Standard work runs 2–3 business days once a legible image of every side is in hand, and the express route brings that in at 24 hours. Getting the copy right at the outset is what keeps that clock honest, because a second attempt at the scan starts it again.