This might be related to the CBS Drama debacle, they moved over to a "new, improved" HD mux, (even though its not a HD channel), and now only 70% of the country can actually receive the channel. We were actually receiving the channel ok until about 4 or 5 days ago, but now its gone.
COM7 & COM8 only have 80% coverage of the UK. These multiplexes are only on main transmitters. See http://www.a516digital.com/p/com7-and-com8.html for details.
https://www.freeview.co.uk/channels-at-your-address/results
says we can get CBS Drama at our address, so something is not right somewhere. I suspect they haven't updated the results with the recent change, but it could be something else. (We are on the Pontop Pike transmitter)