I wrote the British Placename Mapper (https://placenames.rtwilson.com/) last weekend, and it got a bit of traction on Twitter here in Britain over the last week.
It lets you search for parts of British place names, and will plot the places that match on an interactive map, so you can search for places that start with 'great' or end with 'burgh' or contain 'sea' (or you can use regexes for more complex stuff). People have found some cool patterns with it.