final feedback.... I went on the roof, tried to fix it myself by minor adjustments, whilst on the mobile to my wife - looking for guidance when I got a good picture (this did work on a previous occasion about 12 years ago) - but totally lost it ! Lived without Sky for 4 weeks until I could get a professional in - and after all that, he told me it was ineed the trees ! He moved my dish higher about 3-4 weeks ago and it's been perfect ever since ! There are a few morals to this story, I'll let you work them out for yourselves.
Dave, November 2008