I was pleased to find out you can hire these trains out for wedding receptions. I could just see you having canapés on the platform after you have married in one of the local churches or venues and then hopping aboard the steam train for a sit down wedding breakfast in art deco splendour!
You can find out more about hiring one of the South Devon Railways trains on their website at http://www.southdevonrailway.co.uk/hire-a-train
Having a look around there are also several other trains you can have a wedding reception on around the country including the Bodmin & Wenford Railway in Cornwall http://www.bodminrailway.co.uk/private-hire ...
And also the Bluebell Railway in Sussex ... which also has a license for you to get married in their Waiting Room at the station! http://www.bluebell-railway.com/weddings-and-charters/
I hope this gives you a little bit of inspiration for your wedding