I have only ordered one or two cerificates since the price rise and general changes. I know in the past even if you ordered a certificate for John Clark and you knew his name was John Clarke but the GRO had him listed as John Clarke, if you wrote his name as John Clarke in the order, they would not issue the cerificate as it was indexed as John Clarke.

Anyway, I can try ordering the certifcates using last known address. It should work for Mary as she was buried as "Mary Ward" of "Richmond BUildings".

I am not sure if this works if she died elsewhere though her usual address was Richmond BUildings ....
And yes, it used to cost more if you did not supply the reference numbers.
Definitely worth a try though ...
