You're spoiled for choice
Up the coast a bit, around Torbay you've got Babbacombe (which is a lovely site), Brixham Breakwater Beach and Meadfoot Beach to name a few.
Coming down the coast towards Plymouth, you've got Hope Cove, Thurlestone (for the wreck of the Louis Shied), Bovisand Harbour, Plymouth Waterfront, Firestone Bay and Devil's Point (if you're feeling adventurous - but be careful when you dive these last two sites as they're very, very tide-dependant and lie right on the shipping channel out of the Naval Base).
As you're in Cornwall (just) you could try Basket Rock or Hannafore Point at Looe, or Talland Bay.
No matter which direction the wind's blowing, you'll be able to dive at at least one of these sites. Obviously they're all best done on high tide but a few are do-able on low tide as well.