North Coast is the best bet to catch any swell, although dd is right that pembroke will catch the same swells and Ireland should be better still.
Places where you can get suit board hire are Watergate Bay, Polzeath, Sennen, and a host more if you Google it.
As for where to go for a stag weekend ? Your suspicions about Newquay are correct – avoid. You then have a bit of a problem though as you need a bit of life I’m guessing as it’s a stag do. You could always try St Ives which maybe a step away from beer monsteer hell but still have an element of nightlife, should be plenty of suitable beaches with hire etc nearby.