Yeah radiators are the biggest killers of Wi-Fi signals as you are all probably aware. Also you should have WAPs as high up as possible. to allow the signal to go overheads. Difficult to do this in a home environment though. Sometimes you just don't have the choice where you put stuff.
My Mother-in law's house has an extension and if you walk from the kitchen to the extension with a laptop the signal dies instantly as soon as you step over the threshold. I also had to reboot her WifI router the other day - a netgear one.