Fwiw, I never did use the Beresford switch to enable a two-turntable setup. A couple of weeks after starting his thread I decided to go all-out in making a dedicated bedroom system so that I had an alternative room to sit in and listen to music during the hottest spell(s) of summer: my living room typically reaches 27 degrees and stays there, and as I live on a main road, opening the window lets in a lot of noise as well as air, and using a fan shifts air but is noisy.
My Beresford switch is still in its box but I think I'm going to use it to add an extra input to my Rega IO, my bedroom amplifier.