Yeah Wonderland models is THE shop, it takes up 3 whole shop fronts, and should have anything you need. Not much in resin upgrades. Check out their site
www.wonderlandmodels.com There are a few others A2z in Livingston 15 miles from Edinburgh on M8. Marionville models off Glasgow road. It is just past the Shell garage on your right as you head out towards the airport, head for Cargo (turnhouse rd.) its on your right. There is one in Dunfirmline over the (forth bridge) it's close to Dunfirmline Abbey on abbey rd.
Thats all the ones I know of, I live here so if there was anymore I would know believe me. Oh there is Hobbycraft they sell models but not much choice and very over priced. Wonderland would be your best bet.
Enjoy your visit David its a great city.