The language is the easy part
A certified translation in Southampton for Bangladesh has to be into Bengali, because the destination fixes the language before anything else is decided. That much never goes wrong. What goes wrong sits around it: which paper, which version of it, how many sheets, and whether the set stayed together on the way out.
Errors that surface in the first hour
Sheet counts and gaps announce themselves at the quote. Work is priced at about £25 / page, so an extra page is visible the moment the arithmetic is done. A missing one shows up the same way, because the count you give and the scans you send have to agree with each other. Fixing either of those costs a message, not money.
Errors that surface months later
The expensive kind hides. A record that has since been replaced, a certificate that no longer reflects the register, or a translated page that got separated from its signed certificate — none of these stops the work going out on time. They stop the file being useful at the other end, long after everyone involved has moved on.
What a late repair costs
A problem caught here is a new quote. A problem caught abroad is a new record, a new certified copy from Southampton Register Office at 6a Bugle Street, Southampton SO14 2AJ, a new translation and a new wait. An official Bengali translation in Southampton runs 2–4 business days, or 24–48 hours when rushed, but the queue in front of it starts again from nothing.