Congleton is not very big, and won't serve much of a P&R role once HS2 opens, as the car traffic will go to Manchester Airport HS2 instead. I don't see therefore why 1tph (though I'd up Sunday to the same) is inappropriate.
Perhaps extend the southern end from Stoke to Brum via Stafford as a local service, run using long EMUs and priced to push people onto it from overcrowded XC if time isn't a priority?
Of course not as a park and ride.
Services at Congleton are primarily for people living there who want to travel for work and leisure purposes. The ‘car traffic’ is from other parts of Congleton.
No one is using it from far flung places as a P&R.
I think you’re underestimating the size of the town, whilst population isn’t everything, it should be noted that;
Congleton, 26k, 1 tph
Macclesfield, 52k, 4 tph
These clearly do not match for a place of twice the size to have 4x the service.
1 tph is completely insufficient. Any station with similar usage in London/Brum/Glasgow areas would have 2/3/4tph. Why should Tipton (364k usage) have 2tph and Congleton (333k) not? The ideal service would be something like;
Mon-Sat:
1 tph Stopper as currently
1 tph Manc - Birmingham semi fast
1 tph Sundays.
This is the minimum service Congleton should be having post-HS2 as the argument against increasing the current service has always been lack of capacity (except Sundays which should’ve been hourly about 5 years ago).