I spent 3 weeks in Borneo Malaysia a couple of years ago. We spent a week at Sipanan, Kapalai and Lankayan.
Check out
http://www.sipadan-resort.com/
To be honest, if went back there I'd give Kapalai and Lankayan a miss. If I remember correctly the dive sites there are macro dives whereas Sipadan is a haven for the big f**ck off fish. I've never been anywhere where the sheer size and variety of the fish life is so diverse. It's just a shame that we couldn't do a cave dive in the turtle cavern at Sipadan.
I'm not a great fan of "pretty fish" dives but Sipadan is just mind blowing.....very nice people there too. Bear in mind it is a very long journey (London-KL, KL-Kota Kinabalu, Kota Kinabalu-Tawau, road trip to jetty, speed boat to Sipadan). I think it took us about 2 days to get there.
If you need any more info, e-mail me.
Bob