This is what confused me and led me down the path easy peasy
" I reconnected the satellite feeds to the old Sky box, and all seemed fine; channels where expected, I also attempted adding extra channels using frequencies from Astra2e list (high/low, H&V), all as expected. I
checked installer settings, and confirmed the LNB was set up as "Standard" (Low band 9.750GHz, High Band 10.600GHz)."

I would need to see a pic of the lnb to be sure its not a wideband one and the Sky HD box looks a lot different from a Q box.
It will be interesting if it all works with a new lnb but box may have issues from the outset.

And this is a good learning curve even for me