Much as I hate to admit it echokilo....................
You need to get a 'good professional' to come in and properly check the signal strength and tv / recorder setup. I had a similar problem when they first started to added digital. No one would admit the digital signal strengh was minimal and I too pulled out a lot of my hair (which I wish now I had again).
But, I eventually called a well known local TV and Electronics business. The man came out, checked all three tv's and found the signal was so weak that any little change in atmospherics dropped out my picture.
He did a few things and made a few adjustments to the TV and my recorder setup
It cost me £50.00, but in the end I have a much better picture, which should become as good and and as reliable as the current analogue signal, after the changeover in mid-April............
I feel your pain, the best of luck, let me know how you get on,
Old Salt