DMA Design (which later became Rockstar North, developers of Grand Theft Auto) were formed in Dundee. Not exactly the middle of nowhere, but probably not where you'd expect to find one of the world's most popular video game franchises.

Team17 also have a publishing arm in Nottingham, although their HQ is in Wakefield I believe.

Sumo Digital as well although not sure if they make games in Notts - looks like they have a few locations around the UK