Class 502 units were the traction up until mid 70's when the Class 507/508's arrived. At Ormskirk station the electric trains used the bay platform leaving the up and down through lines for express and freight trains.
The stupid, short-sighted decision to cease the use of this route north from Liverpool Exchange station to Preston and beyond resulted in journey times increasing significantly. The main route from Liverpool to Preston and the north changed to Liverpool Lime Street station. A very infrequent DMU service was, and still is, provided northwards from Ormskirk to Preston but with the abandonment of the bay platform and its conversion to become a footpath the dwell time at the single remaining platform has put paid to any hope of change. The remaining left hand side loop track was used for Class 502 EMU's to be dragged north to Preston, then south to Horwich works for overhaul. Horwich works has now been closed and demolished and the loop line track was completely removed creating two totally separate lines into Ormskirk. The route north was then singled with a couple of passing loops so effectively it is a long siding from Preston. The footbridge was also removed as being superfluous.

In the 1960's my brother and I regularly travelled into Liverpool by train from Maghull. The journey passed Aintree loco sheds - at a distance- and we always checked what was there as we sped past. In June 1961 we were amazed to see a red liveried Princess Coronation class loco no. 46238 City of Carlisle sitting down the side of the shed. It was there for several weeks but we could never establish why it was there until an article appeared in "Steam World" a few years ago. All was finally revealed...
Steam World article