I know you have received your certificates since your original posting, however, I will give you a couple of my experiences with GRO ( I live in Australia).
1) emailed 2 requests on same form 5/1/08. Received one 15/1, and now awaiting second.
2) in 2007 emailed a request for certificate. It was in my letter box 5 days later (England to Australia!!!)
3) received a certificate which had the wrong county typed on certificate. Emailed GRO, and amended certificate arrived shortly thereafter)
4) received a certficate, and could not read a word due to poor copying. Emailed GRO, requesting if they could read the word from original. Received an email from GRO 2 days later with correct wording from orignal.
On average most certificates arrive at my home in Australia within 7 - 14 days. Can't really complain about that, or their replies to my emails. I suppose its the same with any Government body, it all depends who receives your request, and whether they're keen enough to help, or whether they treat you as just another "number".
Les