I will be having my ROM at this Axis Bar at Mandarin Oriental next year April. It has a cosy, quiet and relax environment and has a very nice view of the city landscape. They are serving buffet high tea (not sure if there is lunch & dinner) and quite reasonably priced for a buffet at a 5-star hotel, about S$40 - S$50++ per pax with a min of 20pax. An addition set up cost is charged if you need them to set up the ROM table and flowers, sign board,etc. They will partition one corner of the bar for you too. The staff there are also very friendly. If you are interested, let me know, I can send you the contact and a few pics I have taken (though the quality is not very good).