Just saw this on a different forum.
Beware of a website called 'UK Pet Chip Registry'
They will charge you £15 and claim that they will register you pet with something called 'National Pet Microchip Registration database'
It's a scam!
Apparently they've been around for a while so I imagine there's quite a number of people out there who have been scammed by them and don't realise that their pet's microchip has been unregistered for years.