Sky reception?

Since the start of the bad weather here 20/12 I have lost many of the channels, either the picture is pixelated/breaking up, or a message "no signal is being received" The dish is clear of any snow/ice and the feeder cable is in good condition and securely fitted, the box is an Amstrad 550.060 version number 4F0801 with software version 3.8.8

I have tried phoning Sky but gave up after 2hrs waiting for a reply!!

Today I emailed them and got a reply that it must be my box and that they could send out an engineer for £65+ I can't see it being the box as it works on a lot of the channels just not the ones I want!! surely if it was the box it would have problems on all channels??

Since the reply from Sky some of the channels have started to come back but not all of them.

Any idea's??