When the weather is wet and/or windy my BT line is noisy and my BT broadband connection drops constantly. This happens even when I'm using the test socket.

Stangely, when I dial 151 and run an automatic line test the problem disappears temporarily and my broadband reconnects itself. This happens even though the line test reports no fault present. Why would this happen? It's not a coincidence - I've done this 6 or 7 times when my broadband connection has dropped and it's fixed it temporarily every time.

Normally if the noise is only present when its wet and windy there could be potential weather damage to the line outside, the noise on the line would be what causes your bb signal to drop out.

A Line test would normally come back OK for most noise faults as its not a physical disconnection or an easily detectable fault.

151 should raise the fault and ask for a SFI to attend to try and locate the damage to the line.