Yes, the Makerfield constituency is in effect Ashton in Makerfield and the surrounding area.
I believe the name Makerfield was chosen when the constituency contained both Ashton in Makerfield and Ince in Makerfield but the latter settlement has been transferred into the Wigan constituency.
I am not sure if Haydock Park is in the constituency or not. Haydock itself is in St Helens North but the racecourse is located just outside and on the way to Ashton.