Mostly all over fibre in this country nowadays.
As far as I am aware, certainly most if not all of the HD channels carried by Virgin Media are supplied from the TV channels' playout via Fibre to VM where they then get encoded and multiplexed onto Virgin's network, without any satellite being involved.
A lot of SD channels were downlinked from the same satellite feeds at 28.2ºE as used by Sky/Freesat, but this may also have changed to fibre for at least some since they've switched to MPEG4 on Virgin's network (the MPEG2 SD feeds fed by satellite were passed into the VM network without re-encoding when they were MPEG2). They'll probably just get a feed via fibre from Horse & Country themselves.
Way back years ago, in the analogue cable and early digital cable days of NTL and Telewest, the channels they couldn't obtain via the Sky feeds or digital terrestrial tended to be carried on Intelsat 27.5ºW (incidentally, this is still where the encrypted PSB back-up for Freeview transmitters you've mentioned lives), as well as a few other satellites around 34.5ºW-37.5ºW. Channels like Tara TV from Ireland, Performance, and Bravo/Discovery (the longer hours analogue versions that weren't on Sky analogue) were carried on these satellites.
For Freeview, all the transmitters are fed by fibre too (main transmitters), with smaller ones just rebroadcasting a main transmitter off-air. The PSB back-up on 27.5ºW carries BBC-A (PSB1 Mux) and BBC-B (PS
channels with a few limited regional variations (BBC One SD in Scottish, Welsh, NI and network England versions) that get used at some smaller transmitters if the main feed (off-air reception of the parent transmitter usually!) fails. The SDN multiplex (nowadays also referred to as COM4) used to be fed to the transmitters via satellite over Eutelsat 16ºE about 15 years ago but that's long since stopped.
Other countries (France, Spain, Italy, Greece, and some others) mainly use satellite to feed their terrestrial networks, which may be the satellites you're hearing about. These countries use satellite due to the use of large-scale single frequency networks over digital terrestrial - satellite is an easy way to provide all transmitters with an identical feed that can be synchronised. The UK national DAB radio multiplexes are actually fed via satellite (Astra 4.8ºE) for this reason too!