I don't think feasible for 1 or 2 divers to dive labuan from KK - it'll take 3 hours by boat. Sometime ago, I had a chat with one of Borneo diver staff; they can offer for group divers only.
If you want to dive from Labuan, make sure you have firm arrangement. Not very easy to get detail information even you're there although you can easily get a leaflet; but the contact no. (tourist information center) is not very helpfull. They will tell you to go to Labuan International Water Sports Complex. There's only one DS in this complex and not open everyday. They close on Saturday, Sunday and Public holiday. Somebody told me they have an outlet in Tiara Hotel - but again, was closed when we checked last time.
Other alternative you can dive from Brunei - Scubatech Int. at Empire Hotel operate high speed catamaran can reach labuan less than 1 hour.
Some pictures at my galery was taken at Cemen wreck and blue water.