We came across this restaurant in March when we visited the Cricket Inn at Beesands (which also has a very good menu and a light, spacious abience).
Britannia @ the Beach could easily be missed as little more than a shack, but it’s actually a restaurant, and a fish shop, a chippie and a sort of village stores, providing necessaries for the camper vans that line the beach. The food is served almost al fresco, with pride of place going to the fish caught locally by the community in Beesands (so you will never be sure what they might have, but it WILL be fresh!)
It’s not big, but it has a great reputation so booking is to be recommended, but it’s open from breakfast through to the evening. In fact, it’s recently recieved a Great Grub Award from Morrisons (seafood/grill category.
Our recommendation is to park at Torcross or Slapton and walk along the beach (tides permitting) to Beesands – the coast path over the hill can be used if the tide is in.