It’s a tiny ass island yet whenever a British person hears another British person they’ll be like “Oi guvenor! I know exactly where in Merry-ol-England they are from! Clearly they’re from Bovinshire-upon-Weavilton!” And Bovinshire-upon-Weavilton is a town like 10 minutes away from where they live.
And is probably why the east coast has more accent variation in a smaller area. New York even has accents that vary from borough to borough I am told!