Mirrors are a huge part of successful interior design and I've found Exclusive Mirrors to have the biggest range of mirrors I have ever seen, and all for very reasonable prices. (Don't get lost down that rabbit hole, just yet..!)
We used a pair of window style mirrors in the Victorian house in Dorchester, which you can see in full on Houzz, and Exclusive Mirrors wrote a story about how to use them. Read on here:
http://www.exclusivemirrors.co.uk/blog/interior-design-experts-show-how-to-use-window-mirrors/