Poldhu - Porthcurno 28 km (Mount's Bay Dark Water Run) Downwindable.com This is across the very bottom of Cornwall, at the bottom of the Bay and this run does go quite far from shore.
Icon Classic Route (North Devon) Woolacombe - Combe Martin 17 km Downwindable.com
Saunton to Westward Ho! (with N wind - estuary tides can be strong)
Surf
Salcombe Bar shallow, shifting sand bar that can create long, surfable waves video. Needless to say, you have to choose the right conditions - this place can be very treacherous when wind and tide ramp up rough conditions. You may need to know where the shallow rocks are. Nearby beaches (South Sands, North Sands) can get surfable waves also.
Kirton Kayaks Crediton, UK - Boating gear, Kayaks, Epic Surfskis
Surfski Dynamics (Ocean City Paddlesports) Plymouth, Think Surfskis, Guided Trips, also support and encouragement - possibly leads for training workouts, downwinds Devon & Cornwall