Spanish is what Guatemala reads
Files used in Guatemala are read in Spanish, so a certified translation into Spanish in Newcastle upon Tyne is what turns your English record into something an office there can file. The whole sheet crosses over: the heading, the entry number, the district, the registrar's line, the fee at the foot and the words printed inside each stamp. A blank where the English has text reads as a detail you chose not to give.
Months in words, not in digits
The safest date is one that cannot be flipped. Where your English sheet prints a date as digits alone, the Spanish version names the month, which settles the order for good. The same care goes to a year written with two digits and to any date squeezed into a stamp. It is a small habit that removes a whole class of delay, and it costs nothing beyond attention while the page is being written.
The certification Guatemala accepts
What is accepted here is a certified translation with a translator's certificate of accuracy attached. That sheet gives the translator's name, identifies the paper they worked from, states that the Spanish matches it, and carries a date and a signature by hand. No oath is involved. Keep it fastened to the Spanish text and the copy behind it, and hand in the three parts together rather than as loose sheets.
Per-page cost and turnaround
You pay £25 for each page as issued, which makes the total easy to work out in advance: count the sides of paper you are sending, including any reverse that carries a stamp. Standard work runs 2–3 business days once a clean scan is in, and express closes in 24 hours. What lengthens a job is almost always a poor image, because a faint digit in a reference number has to be resolved before it can be copied.
Getting a scan worth working from
Lay the page flat in daylight, fill the frame, and capture the edges where serial numbers hide. Scan the back of every sheet, even one that looks empty. Where your copy is worn or has been amended, Newcastle Register Office issues a fresh copy of a civil record; that office works by post rather than a counter, so allow a few days for it to reach you before the translation clock starts.