Started looking at the Nottingham BBM data. Like Sheffield, a high number of families have one or both parents born outside the city; well at least until the latter part of the 19th century. It's taking some sorting out. a la the Sheffield data, but the Notts data is easier because the base data is available on disc in a very strucured data base (the best I've used to date) from NFHS.
Been in contact with KI and he suggests a timeline would be useful. I'll have a go at one to show when and where Neeedham's migrate to. Should be interesting.