Whatever lights your fire or stirs yer loins. I wouldn't want to add extra bitters to my G&T because I don't exactly hold back on the gin. As for Schweppes, we went to the Plymouth gin distillery and they told us there that Schweppes or Waitrose tonic were the only ones to go for. Mind you, that was over two decades ago... Mind you again, Schweppes always does it for me...