Stayed in Oasis Bungalows in August 2010, while being on Ko Phangan for the full moon party.
Oasis Bungalows in located in central Haad Rin town, 5 minutes walk to the full moon beach and 2 minutes walk to the main restaurants and bars. Despite the central location, the accommodation is hidden away at the end of the one of the roads and is quiet come the early hours (when you'll be sleeping!).
We booked a twin air conditioning room - they are 1000 baht per room per night (approx £20) which is very reasonable for Haad Rin. The two beds are 1 double and 1 single, so you could fit three in the room if on an extremely tight budget. There is a minimum 7 night booking during full moon, but this is standard terms for the town.
Air conditioning was good, bathrooms good and towels were provided. There are safes you can use in reception, which you need a padlock for (bring your own) - this is great for security as reception is also locked overnight.
Overall a great place to stay, at value prices.
Tip for full moon party - ask for no ice in the vodka buckets - it makes you feel awful the next day!