I got my marriage cert from the local Registrar office, and it is this cert which details the religious aspect.
In Carey's and Towger's case, they were married in Reg Office, hence no mention of religion. In hindsight I would have done this if I had realized!
I think I will call DFA and try to get something from them. The problem will be trying to get past the people who answer the phone, and on to someone with some authority. The TD might be a good route too.