Why a Sinhala version travels with your paper
Offices in Sri Lanka work in Sinhala, so an English record on its own gives a clerk very little to act on. The file goes across as a pair: your English paper, or a fresh copy of it, and a Sinhala text that repeats it line by line. Nothing is summarised and nothing is quietly dropped for being minor.
Sinhala, dates and the long family name
A certified translation into Sinhala in Wolverhampton copies dates, registration numbers and seal wording exactly. Long compound family names are a known snag, since a UK form may have truncated one to fit a box. The Sinhala text follows what the record actually says, and where a name has clearly been cut short, that is flagged rather than silently completed.
Who signs it, and what that covers
The certification is a certified translation accepted by UK authorities, including UKVI and the GRO, and it is signed by an ITI/CIOL-qualified certified translator. That page names both languages, lists the pages and states that nothing was added or removed. It stays fixed to the Sinhala text, and a file that arrives without it has no standing however good the Sinhala reads.
Per-page rate and how fast it lands
The rate is roughly £25 / page of source, with 2–3 business days as standard and 24 hours on the express route. A certified translation for Sri Lanka is usually ordered as a family bundle, and putting the whole bundle in at once is cheaper than paying for two small jobs a fortnight apart.
New certified copies, and what Colombo checks
Wolverhampton Register Office at Civic Centre, St Peter's Square, Wolverhampton WV1 1RU issues fresh certified copies of UK birth, marriage and death records. Ordering one means a replaceable copy makes the trip while the record you already keep never moves. That office issues records; it does not translate them and puts no mark on a Sinhala text.
In Colombo the signed page is read first, then the sheets are counted, then names are matched against a passport. An official Sinhala translation in Wolverhampton is held up most often by a missing parent's record in a citizenship file, so listing everything the office asked for before ordering saves a second round entirely.