I have a good amount of info on your Ferriman line. I descend from Thomas Ferriman who was the elder brother of your John Ferriman the miller. I have also been in correspondance with the Ferrimans in New Zealand.
Your John Ferriman was actually baptised in Leicester in 1789, the son of another John Ferriman, a baker, and Fanny Beal. He had two brothers, Zaccheus Duckett Ferriman and David Beal Ferriman.
John Ferriman, the baker, had actually moved into Leicestershire from the village of Barrow upon Soar. All of his brothers also likewise moved away at this time. Thomas went to Spaldwick in Huntingdonshire, and William became a Royal Marine during the Napoleonic Wars.
Before this the Ferrimans had been in the parish since the 1620s, and had probably originally come south from the Southwell and Bleasby areas of Nottinghamshire. Besides the Barrow upon Soar line, another line of the family moved into the neighbouring village of Sileby. On the whole both the Sileby and Barrow families were well to do yeomen farmers. There are numerous descendants from the Barrow family, including some direct Ferriman descendants in Leicester, but the direct male line of the Sileby family appears to have died out in the 1978 with the death of Major-General Eric Mockler-Ferryman.
If you let me know your email I can see if I can send over a gedcom file of the tree.