HI Englishman, Kota Kinabalu is certainly the best destination to start your trip, ( I believe you can get a bus up as well, if you have no one to drive you), you can also get ferries that go that way. (not expensive and safe, Brunei makes sure the Malaysian registered boats conform to International standards or they are not allowed in Brunei waters.
Fromr KK you can take trips to the Jungle / rainforests and the Orangutan sanctuary's), the roads are fine in Brunei itself, (i havent driven up to KK, but i have a few friends who have often, and they said its no problem.
Hotels are expensive in Brunei, but there are deals to be had sometimes. (If you let me know nearer the time, I can see what I can do at the Empire Hotel. (place is stunning), and i can normally get it for 80 pounds per night. The biggest problem with Brunei is getting around, you really need a car as the local buses can take forever, (car rental isnt too bad at 30 pounds per day) I can give you a number if you need this. .
http://www.asiaexplorers.com/brunei/kuala-balai.htm , this is a strange day out, never seen so many skulls before!!, if your base is Bandar, catch a lift to Kuala Belait, and get the ferry form there (much cheaper), there are hotels up in Kuala Belait as well, but they are expensive (and crap) as its near Shell Brunei's headquarters. I would have offered a a rorm at my place but we will be away form here by then. (plenty of pinoy's in Brunei)
ENjoy your trip, let me know if you need any more info on Brunei and I can try and help
