Thanks BippyM. Haven't tried ReSource in hi-res yet but I will do when I get a chance.
On the subject of disassembling games I came across this guy's site yesterday:
He's done a cross platform version of Frontier by disassembling the code, pulling out the OS calls and other hardware specific stuff and writing a program to convert 68000 asm to portable C. Interesting approach. The source code to the asm to c converter is there but I haven't looked at it yet.