"Anthony Frost" wrote ...

Computerised lists and repeated nagging by post if an address
doesn't show up as having a licence mostly.

Tell me about it. Thanks to incorrect address data in their system
my parents, and their next door neighbours, have been getting
repeated 'warning' letters and no matter how many times we tell
them we've paid and got the papers to prove it they haven't got
their act together.

There are a number of
detector vans, some of which actually do have equipment inside, and a
larger number of hand held detector sets.