Thanks for the replies girls.
Just to give a bit of background, from my point of view, and I should also say my partners point of view, as much as it would have been nice to change my birth certificate, we were not prepared to change the marriage record in order to accomplish this. As far as I was concerned the important records such as passport, bank, employment, doctors and driving licence etc have been done. The only other record that would have remained 'male' would have been my death certificate and I wouldn't have been around to complain about that.
Now that the Equal Marriage act has arrived, I can get a 'full house', so to speak, without any undue stress (on myself or my partner) as the important thing for us is that we got married and, luckily, we intend to stay that way. An annulment would have been catastrophic for our relationship.
Would adding gender and sex, or, 'acquired gender' and 'birth sex' to cater for the whole load of genders and the biological sex assigned at birth on these records be helpful? Would it be better to simplify things and offer just 'Man' and 'Woman' or 'Male' or 'Female' as genders and leave it up to the individuals to apply to change this if they want. For some, this would be a case of one partner/spouse persuading the other that this is what they want etc.
Anyhoo, thanks again..

Nikki