Thanks to all for the above feedback. All is correct; military does indeed fly down to 250ft and the only fuel north of Blackpool is the man-and-a-bowser at Kirkbride.
For information on military low-level flying, you can call the RAF’s Low Flying Booking Cell (info below)
Low Flying Booking Cell
01489 443093
MF 0700 – 2300
For low-level military flights on weekends, they say to call them on Friday afternoon and they have all info for the weekend.