I have been told that John Wesley read the pre-Schism fathers a lot, and was influenced by them.
Is this so, and if so, to what extent and how was his doctrine influenced by them?
Interesting question. Wesley, as an Anglican, would have learned to understand Scripture through the lenses of Tradition and Reason. Tradition for him would have included everything from his contemporary Pietists back to the early church fathers.
I did a quick search and discovered that Wesley believed those closest to the beginning of the church had an advantage over modern Christians:
Can any who spend several years in those seats of learning, be excused if they do not add to that reading of the Fathers the most authentic commentators on Scripture, as being both nearest the fountain, eminently endued with that Spirit by whom all Scripture was given. It will be easily perceived, I speak chiefly of those who wrote before the council of Nicea. But who could not likewise desire to have some acquaintance with those that followed them with St. Chrysostom, Basil, Augustine, and above all, the man of a broken heart, Ephraim Syrus. [source]
Wesley's teaching on Christian Perfection was partly influenced by his reading of the fathers, and his doctrine of Prevenient Grace appears to have been derived from Chrysostom; beyond that, I'm not sure how much he drew from the ancient fathers. The primary influences on his theology would have been his contemporary Pietists as well as the writings of Jacobus Arminius.