About 20 miles. But accents here change a lot in short distances because of the large local communities. For instance Birmingham and Black Country people might sound very similar to people outside of the West Midlands because they are only a few miles apart but we can easily tell the difference. I've had many people ask if I'm from Birmingham, but our accent is weird and only partly Brummie.
Can't wait for this. Accents are a bit off but I suppose only local people pick up on that. Or as my workmate calls them, "stupid fucking yam yam speak".