The champagne was free-flowing at the Ritz Carlton Club Lounge, The Fullerton Straits Club, and the Conrad Executive Lounge when I have stayed there. Fullerton and Conrad serve Veuve while the Ritz serve Moet. The RC, however, do serve cocktails between set hours made by a dedicated bartender in the Lounge.
I cannot comment on the champage at the Oriental Club -- I was not there long enough to observe what they were serving. I have not stayed at the Shangri-La Valley Wing nor the Regent yet so I cannot comment.