Years ago I asked this question and got a brilliant recommendation for Blacker Hall Farm shop which has become our usual stop off place between my parents and our house. We've been there umpteen times and it's always been a happy break.
Today though we'll hit it at Sunday roast time where all we'll want is a coffee and a cake.
I'm looking for new places to try that are less then 10 minutes drive from the M1 and serve reasonably decent coffee. Clean toilets and something to wander around (little walk, or a playground or a garden centre maybe). Ideal stopping point would be between the start of the M1 at the Northern end and definitely no further south than Nottingham.