I've lived in the MK area for 20 odd years and this is the first time I've heard the words "Bletchley" and "decent places" in the same sentence.
There's a pub by the bus station (The Enigma) which is an experience. There's a Burger King next door to it.
There are a couple of curry houses under the flyover on Duncombe Street (There used to be a pub there too, The Park, not sure if it's still open though. Last time I was there, I had to serve myself as the barman was otherwise occupied with one of the local ladies).
There is/was a cafe/chip shop in the Brunel Centre, haven't been for a while but the food was OKish.
Otherwise head down Queensway for non-chain burger bars and lots of charity shops.
The problem with Bletchley station is that the entrance is on the wrong side for easy access to the town.