This map shows fieldnames as collected on OpenStreetMap.
It also shows church sites, ringforts and castles (from the same source) to illustrate the correlation between those features and fieldnames.

Legend

Fieldname Fieldname as surveyed recently and still in use.
Fieldname Fieldname in historic source or historic use, i.e. field is no longer in existence.
ringfort
church (in ruins)
castle (in ruins)