It can be flown in, but that relies on: A) Extra Canadian capacity (which isn’t a given considering how reliant USA is on the same reactor) B) the NHS having the extra money to pay for more expensive isotopes (it doesn’t) C) getting through the same customs delayshttps://twitter.com/JonMarcStanley/status/1103298900126060544 …
It's a flight cost. For certain items HMRC can work to ensure any checks are minimal and usually electronic. For flying in moly cows i cant see a big variable cost in the grand scheme of things.