They'd be swapped at Carlisle with fresh units off Neville Hill or Heaton, I'd have thought. The daily mileage shuttling to and from Carlisle wouldn't be too high (there'd be a lot of 'standage' at each end) and 156s can do around 1000 miles per tank.How do the units at Workinton get fuelled and so forth? I guess there is some contingency being worked out of how the units are cycled through exams from now on.
But yes, it's likely to be a bit of a pain for Control as they'll be needing to do swaps more regularly than the normal unit diagrams assume.
