Derbyshire
I visited my first St Mary's in Derbyshire when I went to Staffordshire in February 2019 and my "associates" got it wrong (again) and thought Marston-on-Dove was in Staffordshire but then found it's in Derbyshire (something to do with the side of the river it's on). It's got a bit complicated 'cos I've now also visited Rolleston-on-Dove and that IS in Staffordshire!
But I've now been back to Derbyshire a few times (I said I would) and have added more lovely St Mary's churches to this list.