Kohphangan's climate is the whole year beautiful. Nice weather days and a nice sea breeze are the norm. The best time for a visit, end of December to late of March will be the best holiday Koh Phangan is the main Koh Samui.
On resorts on Koh Phangan on www.PhanganBungalows.com. accommodation at Phangan, I can suggest you the B52 BeachResort Phangan, not distant to Thong Sala, the biggest village on the place. From B52 guests have an uncomplicated access to restaurants, banks, money exchange and mini marts.