Thanks for the ideas Bob!
Yes it looks like the Xpander uses 2 MHz 6809 processors ('68B09'). Mine has Hitachi's in them (HD68B09P); I ordered some new ones on Ebay just now. USD 30 including shipping to the Netherlands (but excluding import duties... will see).
I think I will manage popping IC's in and out of sockets but burning EPROM's would be a step up for me. I think I would rather buy a set of pre-burned Xpander EPROM's on Ebay, which is doable (USD 65 ex shipping it seems).
I am going to try swapping out the CPU's before I move on to the OS EPROM's.
Cheers, Jacob