Good point on the weather... interference and weather are the front runners. But you're right - I hate not identifying the problem. I share your enthusiasm for debugging - if I discover anything helpful, I'll post it here.
Meanwhile, it's been a while since I've looked at the digital broadcast websites, but they don't seem to be as well maintained as I recall. The broadcast power from Hannington is apparently incorrect for COM7 and the OTA update info at http://www.dtg.org.uk is well out of date... maybe updates aren't as regular as they used to be?
