For England and Wales you can buy a copy of the marriage certificate either from the register office in question or the General Register Office. The GRO has a website where you can purchase certificates. All you need are the names of one or both of the couple, the name of the district, the volume and page numbers - these are the ones you have already found.
The local register office, where the original will be held, is a bit more tricky as a lot of offices have 'moved' with local boundary changes so tracking down where the register is now held can be awkward; and a lot do not allow on-line ordering. If you do find the correct register office, the volume and page numbers you have found will not apply; those are only for the GRO.