Many thanks for your kind help.
I now understand that it should be a ipk file to upgrade my boxes, but I'm still wondering if there is a general problem with the channels I mentioned or if it's just my own incompetent setting up?
I should have mentioned before maybe, but it's a VIX image I have, but I'm quite comfortable with the process to upgrade either with the box's plugins download facility (when available) or by the VIX "install local extension" system. It's just that there seems to be such a wide range of different versions of each version that it becomes somewhat confusing!
Both my boxes have an ARM processor, so do they both use the same oscam? I saw one version somewhere that specifically mentioned "HD51" in the filename but couldn't get it to work in the Mutant. May be just my error, of course...
Anyway, thanks again for your help