In the event you're applying for an Ancestry visa and require your grandparent's birth certificate, how can one get an official copy of said certificate that would be acceptable in an application?
I had to do this for my Ancestry Visa application. My relative's certificate was not easily accessible to me, so I found out that it's possible to order a copy of a birth, death or a marriage certificate online.
You’ll need to register on the General Register Office (GRO) website to order a copy of a birth, adoption, death, marriage or civil partnership certificate in England and Wales. Certificates cost £9.25. You can use this service to help you research your family tree.
There's a different process for Scottish and Northern Ireland certificates, linked to on that site.