Update.
I tried STEP and IGES exports from BCC, opened in MOI, deleted some duplicated, vertically translated objects from the IGES version then saved out from MOI as STL.
Loading the STL files into netfabb showed both with some issues but netfabb was able to auto-repair the better looking of the two, the IGES format.
The print came out spot on!
Thanks again for your help with this! I'll try a few more test parts and if all goes as expected I'll be buying an MOI license and then some printable wax, I might get some use out of my foundry equipment yet!
Regards,
Nick