I have done it!
In a sea of strapless floral nightmares I have found a dress that actually suits me. I ran towards the changing room with silent tears of joy sliding down my cheeks, embraced the assistant and swung my bag happily on my 'result' after purchase. I am resigned that in 10 minutes everyone else would have brought it too, but I am still happy. I also got a pink, smock-y, lace-y top thing which sounds horrible typed down but is actually really cute, and 70's ish.