Bob, It would appear that any tours that you wish to go on may have to be pre-booked(on-line in Oz)--eg. Open double decker bus tour of Singers, Changi Prison and others but not for Sentosa. Perhaps avoid booking tours direct with the Hotel as they may load the actual cost. I also remember that when you make the trip over to Sentosa Island you can book multiple attractions for much cheaper than paying individually. Just something else to consider. I would add to the list, Singapore Zoo you can pay at the entrance. Also, consider boarding the Singapore Flyer(no need to book) a huge ferris wheel overlooking Marina Bay(the same size as the London Eye). If you go to the Raffles Hotel Long Bar, don't be surprised if the cost of a Singapore Sling seems steep at $25 plus each but are well worth it and after 2, cost becomes no object-lol lol. When in Singers Airport (airside) for your return trip, take note of the cost of alcohol before you order-- be careful and look at the beer menu charge etc. and they add 17% service charge and tax on top. It's in the small print on the menu. Last year I slipped up and we were charged all up $32 per pint. Thank goodness I only had the 1 pint. Look for a Harry's Bar or make sure you have your wits about you--same with airport food. Sometimes it's better to have Hungry Jacks (Burger King), McDonalds, Pizza Hut or Subway in the airport. Once bitten twice shy.
Cheers Aussie 1