Sorted it. 
I couldn't get the compression identical to the original files, the closest I could get was by setting the windowbits to -8, the memlevel to 1 and using the fastest compression preset. I could've made the GZip'ed files for MI2 much smaller but I assume that the game has the larger filesizes for a reason - possibly a tradeoff for less memory needed for decompression.
Also - SKA-T - I've got your email, I'll post your stuff up tomorrow