Something I was wondering is how much it costs to transport all those cows to the other end of England compared to sending the existing ones to slaughter and buying a new gang once you've arrived at the new farm (and built the parlour). What is the shelf-life of a dairy cow anyway?
Definitely better to transport them! 200 ish cows worth at least 1200 each = £240K. Transport, probably 25 - 30 cows on a big artic stock wagon, so 4 - 6 loads, plus young stock, I would guess maybe £6k to £8k (and I do mean guess, it's a while since we've transported any cattle very far, so I can't remember actual figures.)
You would never slaughter them to replace them up north anyway, they are worth more sold as milking cows. But it would be unlikely anyone would sell their established herd in one county to buy another elsewhere. You would be bringing in all sorts of unknowns in terms of disease, the dreaded TB being the main one, but there are several others. The only reason to do it would be a complete change of cow type to suit a different system (going from intensive Holsteins to grass based cross breds, for example).
I need to listen to tonight's again, trying to listen when the kids are in the bath is tricky!