I have had absolutely the same problem since I intalled the update to WP 8.1. With WP 8.0, both in my former Lumia 920 and in my current Lumia 1020, I simple told the phone never to disconnect from the WiFi network, but now this setting is gone. I got an iPhone, because I cannot live with this very annoying malfunction. I have tried every solution I found in the fora, all to no avail. Horrible, horrible update!!!! I am planning to send my phone to the warranty service, but this is really idiotic.
