To be honest, I don't know why gay people are so interested in wanting to get married, because of the highly religious connotations, and the typical religious persecution that usually comes with it, I would have thought most of them would want to distance themselves from it.
This is very much a misconception pedalled by the religious, marriage in the UK isn't a religious thing, it is a civil thing. The only religion that is allowed to perform marriages without a civil registrar is the Church of England. Every other religious wedding has to have a civil registrar present or they have to have a separate civil ceremony.
More civil weddings take place in the UK now then religious weddings. Especially since many more places can allow weddings to take place. It is no surprise that most people chose "picturesque church" over "60s registry office" when those were the only two things on offer.