Don't worry, I had the same problem and must have tried on about 50 dresses too. I couldn't find a dress with everything I wanted. I went to see about getting a fairly plain dress made and they wanted £950 which I really couldn't afford.
So what I did is I did a lot of research on the internet and found a mori lee dress that I liked. I hadn't found anywhere local to try it on, and I decided I would go to 1 last shop. I went to the shop and believe it or not they stocked it. I tried it on and knew it was the dress for me. But I didn't order it from them, I ordered it from
www.rebeccarode.com and it only cost me £250 instead of about £850 plus the rest.
I was going to order the dress even if I hadn't found anywhere to try it on. I really recommend that you look on their website for dresses in the style that you want and see if there are any you like. You may even find somewhere locally to try it on before you order. They will not allow you to order it from them if they don't think that they can deliver.
The other thing is, aren't wedding dresses designed to be altered up or down 1 or 2 sizes? Could you perhaps see about getting the next size up or down at Debenhams?
I really feel for you and hope you find the right dress soon,
Hx