We're on a budget, and like you I am short, and a size 16-18. Wed2b is great for budget friendly wedding dresses, its where I got mine. My bridesmaids and flower girl dresses have come from eBay, as have my shoes.
I've used charity shops for decorations, guestbook, photo albumn and anything else I can get my hands on!
Top tip for your cake - M&S!
Hope this helps!