As far as I know, the earliest home soundtracks are from The Daleks. But there might have been overseas recordings (and they might be from repeats: the home movie off screen bits from season 3 definitely look as if they were shot during a repeat, so the cameraman knew which moments he wanted to get)
Overseas I could buy, but I thought repeats were extremely rare. When they reran "The Evil of the Daleks," it was so unprecedented that they actually set it up at the end of "The Wheel in Space" as a mind-recording the Doctor was showing to Zoe to warn her what she was getting into.