@ Channel Hopper
It's only the two you know about! I was just remarking that some of the problems over the past few weeks were cured by replacing the LNB.
What I can't understand is why the failure to lock on is not consistent across all V polarised channels. Unless it's frequency related, as you suggest. I suppose I'll have to go out in the rain and wind, up onto the garage roof, exchange the LNB's and then fiddle with the Humax to find out which channels are affected. Hmmmm. On the other hand, I could just sit in front of the fire for the afternoon.