Before May 2018 there were only 2tph via Atherton (3tph peaks only), one Vic - Southport and one Vic - Kirkby. But there were 3tph on the Weshoughton line, one Airport - Southport, two Vic - Wallgate. Now there are 3tph via Atherton, one Leeds - Southport, one Blackburn - Southport and one Vic - Kirkby, but only 2tph via Westhoughton, Stalybridge - Wigan NW and Alderley Edge - NW. An increase to 4tph via Atherton was planned from this month, the 4th service being Vic - Wallgate, but Network Rail has vetoed this because of performance concerns in Manchester. Instead the Kirkby service is being split into separate Vic - Wallgate and Wallgate - Kirkby services (I presume to enable the Vic - Wallgate diagrams to be strengthened to 4-car).
So Wallgate will be terminating 1tph from the east from 20th May with 2tph to North Western.