This will hopefully help and shed a bit of light on what's been happening. Astra 2g was activated around 8 weeks ago and some channels were moved onto this unexpectedly, this is the final change now as far as i am aware. All the itv hd's, channel 4hd/4seven, bbc news hd, the whole 5 group. This will explain the sudden loss of some channels for those with smaller dishes. This satellite is now coming to the end of the settlement period and the powers should match those of the other 2 satellites. Channel 5 came back on a few weeks ago, 4hd came back last week but is still a bit in and out and itv hd is in and out at the moment. I have also noticed the powers vary more now than before form village to village.
The other thing they have done is move 2e to 28.5 (0.3 degrees) this means smaller dishes won't be able to grab all 3 satellites. Luckily 2e has most of the bbc, itv and channel4 's on so a tweak can get these back. Where i am tuning to 28.5 got most of the channels on an 80cm dish but this doesn't work for everybody and there is no give for rain and cloud.
Another thing you can do is buy a raincover from the internet. This sits over the lnb and stops the rain landing on it which is 80% of the problem solved when you have light/medium rain.