Tricky, without giving you a botany lesson!
The photos below are of what I had in mind. They are scaly male-fern, Dryopteris affinis.
It's a very robust species that has thick and heavily scaled lower stems, and the upper surface of the frond is glossy. During the growing season, mid-May to October, these plants would be around 5 ft tall. It grows on mildly acid soils.
If you want to take the i.d. further, on this species there is normally a dark spot on on the underside of the frond at the junction of each little green "leaflet" and the stem it is attached to.
The old fronds persist until new ones start unfurling around early May. By comparison, the common and rather similar male fern Dryopteris filix-mas will have died back and gone golden brown by January except in sheltered spots in woodland etc.
A common species in the south-west where you are is the soft shield-fern, Polystichum setiferum; it grows on more limey soils. This is largely wintergreen, and each of the little green "leaflets" (correctly called pinnules) is somewhat sickle-shaped, with a point at the tip and a blunt thumb at its base.
See if you can borrow a copy of "Ferns, Clubmosses, Quillworts and Horsetails of Cornwall and the Isles of Scilly" by R. Murphy and others (2012) from a library.