Would second the above recommendation. Some fab downhills into Porlock. Also some excellent semi-coastal trails around North Hill / Selworthy Beacon on the opposite side of the valley- epic views too.
Not ridden the bridleway down from Selworthy Beacon down to Lynch Combe yet (N of Bossington), but walked it a few months back and I reckon it would be a hoot on a bike.
Some great, proper old school, all day XC rides to be had by following the network of bridleways around the Exe Valley NW of Dulverton – river crossings, hike a bike and some great singletrack – Riding your bike across Tarr Steps is an unmissable experience, especially with the river in full flood! You can ride onto Withypool along the river then up over the top of Winsford Hill to the Punchbowl. Quite a few trails radiating out from Winsford itself too.
Just get an OS map and enjoy… great area for the adventurous, and you’ll see very few folk.