Bayonne's is decent, but IMO the two best putting greens around are Walton, which has already been discussed and Royal Wimbledon. Royal Wimbledon is the venue of the public schools old boys putting competition and it's perfect for it. Both are about the same size and both have plentiful space for 18 holes of putting on them. Royal St Georges isn't bad either. All three have had many the putting contest for a pint of something ill-advised (kummel springs to mind).