There is a loose theme with the cross country numbers.
M31 is fast Manchester - Bristol
M33 is fast Birmingham - Cardiff
M34 is a coach on the Manchester - Birmingham - Oxford corridor
M36 is on the Manchester - Birmingham - Bristol corridor.
There are too many stopping combinations to give everything it's own number
M31 is fast Manchester - Bristol
M33 is fast Birmingham - Cardiff
M34 is a coach on the Manchester - Birmingham - Oxford corridor
M36 is on the Manchester - Birmingham - Bristol corridor.
There are too many stopping combinations to give everything it's own number