Film4 +1

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
47	everywhere it is carried	COM5 (ARQ A)	DVB-T	16:9 SDTV

On COM5 (ARQ A)

92 transmitters radiate COM5 [V] — the main stations only, not the relays. By nation: England (66), Scotland (14), Wales (9), Northern Ireland (3). It is operated by Arqiva.

If this is missing, so is everything here

28 other services share COM5. 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.

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