Cockadoodlequack One of the debates they're having at the moment is whether to extend civil partnerships to straight couples.
So, at the moment:
If you're gay, you have a civil partnership.
If you're straight, you can have a civil or religious marriage.
I've honestly lost track of what they are trying to achieve now. I think it's civil partnerships for straight & gay, and marriage for straight & gay with opt-outs available for religious groups that wish it.
As for mentions of religion, maybe it depends on how much the registrar is willing to overlook? We have to submit copies of all the readings and songs were are planning to use in advance to make sure they are suitable. Quoting directly from the email:
"Please ensure that you do not incorporate anything of a religious nature or any religious connotations. For example, the words, "?to have and to hold, from this day forward, for better, for worse, for richer, for poorer, in sickness and in health, till death do us part" are from the Church of England Common Book of Prayer, so therefore cannot be included in a civil ceremony as they stand."