TBN UK

Logical Channel Numbers are assigned by the platform, not carried in the transmission, which is why they differ between nations and why a retune can move them.
Channel number	Where that number applies	Multiplex	System	Format	Availability
66	everywhere it is carried	PSB3 (BBC B)	DVB-T2	16:9 SDTV	on some transmitters only

On PSB3 (BBC B)

1,127 transmitters radiate PSB3 [V] — nearly every television transmitter in the country. By nation: England (638), Scotland (236), Wales (205), Northern Ireland (48). It is operated by BBC.

If this is missing, so is everything here

15 other services share PSB3. A multiplex is one 8 MHz transmission carrying all of them at once, so it arrives whole or not at all — losing exactly one of these and keeping the rest is a fault in the channel, not in your reception.

BBC Three HDBBC Four5SelectU&EdenLegend XtraBBC One HDBBC Two HDITV1 HD / STV HDChannel 4 HDS4C HD5 HDBBC Four HDBBC Scotland HDCBBC HDCBeebies HD

Which multiplexes should reach a particular address is the postcode lookup.