Not yet (short of my son's unfinished small loop type layout but it's very much a kids type arrangement with 2nd rad curves).
I too have a shed down the garden (about 10x10) where I might be able to do something, but I suspect as soon as I finish the floor it'll be filled with son's fishing stuff, gardening bits, etc... I'll be lucky to have a workbench!
Also not sure of where or what I would model in there (maybe something like Westerham?, but it's been done before, and sometimes it's nice to just watch trains go round and round until you're dizzy

).
I have a very good idea of another layout location which would suit, and I think I could fit it in the loft, but the loft is also full of a lot of rubbish that my wife won't chuck, and I need to finish the last quarter of the boards and insulate between the roof rafters to try and control the cold/heat...