Many thanks for these suggestions guys. I will put a meter on the dish and trying tweaking it a bit, as over the winter we had a "Super Mistral" at 175+ KPH and this may have moved the dish a bit. However as my BBC seems spot on it cannot be too far out. I think I am more on the edge of the lobe for ITV than for BBC.
I know that these gas valves may give me a bit of signal deterioration. The first one (the earth shunt) is made by Foudretech and costs an eye-watering €200. The second one is all part of my Monster Cables power cleaner/surge protector and again is about €300. I lost about €6,000 of audio/sat/TV equipment in the strike last year and I don't want it to happen again. Luckily it was all insured and as I had all the other lightning precautions in place, the insurance company were not tooooooo difficult. It was the first time in about 20 years that the adjuster had seen a dish struck. It melted the LNB off the front of the dish and where the cable was in a trench from the bottom of my garden, it opened up the trench along its length and turned the cable into confetti. The Sky box exploded in front of my eyes - quite exciting. My house is about 2,200 feet above sea level and is built on the edge of a 1,000 foot high escarpment, so it is the first thing that storms sweeping up the valley will hit. I therefore have at least two layers of lightning protection on everything. I have a large box in my cellar with 4 surge capacitors in it, one for neutral and one for each phase plus an earth shunt cable about 3/4 inch in diameter, for the mains power system. This will absorb/shunt up to 10 strikes before the capacitors have to be replaced (they have tell tales on them).
I have had a firmware update on the Humax box since I came down in April and done a retune recently, so I don't think it is that. I saw on another forum that the Humax box defaults (due to my entering my Sussex post code) to the north lobe for ITV and it may be possible to tune to another lobe, which gives improved reception in the south of France but that forum gave no further details on how to do it (frequencies etc).
Wilson