It now appears to be fixed thanks. I was able to sort it myself and cancelled the engineer visit. As I was advised over the phone, it was likely a loose cable or, more seriously, a failed cable with the coaxial being the likely culprit. In my case the coaxial has an added extension to reach the V6 converted to 360 box. The nut connecting the extension had worked slightly loose. I tightened it and all the lost channels came back. That was nearly a week ago and so far, so good.
