Welcome to the site GrayIsTheNewNothing! Unless there's actually an event on while you are here, I'd suggest you visit Wincanton in Somerset as it officially twinned with Ankh-Morepork. The Discworld Emporium is right there in the High Street and you can buy lots of DW related goodies there.
Once a month in London a group known as the Broken Drummers
meet up in a pub for a social gathering and chat about Discworld. If you aren't already getting it, you might want to subscribe to Discworld Monthly
as that will give you all sorts of information about Discworld events in this country and all over the world.
Hope that helps.