Freesat box

We had trouble with our Freesat signal and it seemed worse in bad weather. We called an engineer and he changed the LNB (Low Noise Block device - sits on the end of the arm in front of the dish and collects the signal). LNB is particularly vulnerable to weather and we could see the damage to ours. The work wasn't expensive and we didn't need to change our Humax/Freesat recorder. It all works fine now.

I think your box may be failing. We had similar trouble with our Humax freesat box earlier in the summer. It became slow and sometimes unresponsive. I thought that it was a problem with the remote control and ordered a new one.
The very next day I was watching the tennis from Wimbledon when the picture froze and the screen was covered in pretty blue and pink pixels.
Happily, we haven't needed to replace the freesat box. Our tv is only a couple of years old and came with a satellite decoder built in. Our son came round and hooked the cables up to the TV. I would have done it myself but his fingers are more nimble than mine.

We have a Freesat box here in France. We get interference as you describe or lack of picture when the weather gets a bit iffy. Sometimes the weather seems OK and the picture comes and goes but most of the time it is fine. Is your dish big enough? We had to get bigger dish when they moved the satellite a degree or so.