I'm the same age as Snoozy and from the UK and would never wear that dress to a wedding regardless of if it's being held in a church or not. As a general rule I think your dress should be at least knee length and if the ceremony is in a religious place, your shoulders and cleavage should be covered as a mark of respect, regardless of whether you are religious or not. A wedding is not the place to be sexy and even if it is, you can be sexy without showing that much skin. That's the kind of dress you would only wear at a hen partyCan someone who attends a lot of weddings in the UK clarify whether that silky peach colored backless dress is something that people would actually deem ok for a wedding? I don't think anyone would consider attending a wedding that naked in my country but maybe it's a cultural difference? It looks a little offensive and scandalous to me and I'm not a Mormon or anything.
Especially if you don't even belong to the family of the bride or groom and are attending the wedding as a friend, it seems very inconsiderate to draw that much attention and upset the grannies with your freed nipples.
Also what idiot wears high heel mules to a wedding, not appropriate for dancing and not the most comfortable for wearing all day