AFAIK they're pretty much obsolete, but might be wrong, there's a
newsgroup, uk.rec.radio.cb where you can get the proper answer, this
question is asked regularly there so a search on google groups
restricted to that newsgroup will get the answer quickly, use the
"advanced search" option.

Larry came up with the following;:

Potentially still useful .. but ...

We use an old CB, technically illegal I believe as it's an old AM rig, along
with some mates.  They're great for keeping in touch whilst off-roading or
simply driving in a loose convoy.

We all keep meaning to get up to date with new legal rigs, but wtf, the
amount we use them it hardly seems worthwhile for the cost of replacement,
and we've never heard of anyone being 'done' for using them, though i guess
the fines may be exorbitant.

Turned it on yesterday and it was full of foragers with a few locals trying
to get through and I still have a licence for it.