There’s a website www.ontimetrains.co.uk which ranks stations by a performance score, which is calculated based on service punctuality and cancellation frequency.
So, on the list of worst of all 2,615 stations in Great Britain for punctuality and cancellations, taken over the past 6 months:
1st: Slaithwaite
2nd: Mossley
9th: Greenfield
17th: Marsden
42nd: Stalybridge