I'll do one for you if the wedding is in NE Lancs. The Rapido Man has contracts all over - he might be worth a try.
I don't know where the releases originated. It is big in the States and I know that they do them in Greece too.
The Dove symbolises love, peace and new beginnings and of course they pair for life. Some people even theme the whole wedding around the doves.
You could release the birds from a display cage or a heart shaped basket or, even each hold a dove and release them together. You could then have another basket with a dozen or so birds in and release these to represent the love of your family and friends.
The photographer needs warning how fast the release is and, I always take a spare pair of birds lest, as has happened :, he misses the birds entirely!! ;D
Sue