I’m from Shropshire, and it nailed that reasonably well, although there was a big stripe across the black country and into the East Mids which seems quite odd. It specifically excludes Birmingham though.
Most obvious giveaway for me was ‘island’ to mean ‘circular traffic junction’. I didn’t even know that was a regional thing until now, but it seems to be centred on an incredibly small area
Interesting too that my mum is Irish and it showed that some of the words I use are most common in Ireland, but in the final shakedown it didn’t try to place me there at all.