The paper I was sent about 2 months ago says the following.
507020,028, 508103/110 are priority classified mileage units and need to be kept spare or put on the lowest mileage diagrams - no weekends
508108, 114,134,136,139 also priority classified mileage and to be kept spare at weekends. 134 has 1700 overhaul miles left and will stop at 250. To be kept on Southports only and stabled after peak.
Like I say this was a couple of months ago now, probably November
507020,028, 508103/110 are priority classified mileage units and need to be kept spare or put on the lowest mileage diagrams - no weekends
508108, 114,134,136,139 also priority classified mileage and to be kept spare at weekends. 134 has 1700 overhaul miles left and will stop at 250. To be kept on Southports only and stabled after peak.
Like I say this was a couple of months ago now, probably November