FWIW I've managed to set up a work-round based on editing the aliases.conf file. I use crossepg and aliases.conf is in /usr/crossepg/aliases. I simply added lines specifying the NID,TSID and SID of each source channel (Freesat) and the corresponding destination channel (Freeview) and when crossepg downloads the epg, either scheduled or ad-hoc, it copies the info for the specified channels from the source to the destination. It's not perfect - I had to suppress eit epg display in the info-bar for example, which affects all channels on all satellites - but it is an acceptable work-round for me at least.