Some of the latest taxonomy actually suggests that chats are very closely related to flycatchers, so some would argue that you were right KK.
Among the features that identify this as a female stonechat are:
Comparatively long, strong legs (compared to a flycatcher)
Comparatively strong bill
Streaked upperparts
Warm orange rump
Warm orange-buff breast
White throat/neck
Contrast between paler supercilium and darker ear coverts
As well as the posture and habitat, as Gary mentioned.
