Fixed it from settings did a Satilite scan everything working well now.
We too regularly lose Bravo and Prime and when I've remonstrated with Dish TV they just brush it off as a dish or LNB problem. But .... if I reboot the A2 Box then the channels come back again, which suggests to me it is not a dish problem. Further, we have never had this problem until we bought the A2 SuperBox, which also has other issues. I am sure it has been released to the market before being developed fully.
A full power-off reboot seems to do the trick which is probably quicker than re-scanning. It is a bit of a fag though as it takes a while, also loses your On Demand login whicht needs to be input again.