It's been a long time, however I've not given up. I've moved to a new city and it just so happens that this new city has a hackerspace that gives me access to a few cool tools; namely a lathe, a mill and a laser cutter. As a result I've come up with a good way of doing the wheel/pulley/motor assembly.

http://imgur.com/a/HKiDT

I need to do a few more steps before my first assembly is complete but it should be easy once I get the supplies.

My next major task is to try and get the Hardox armour plates ordered. I don't want to build the chassis only to find that the armour doesn't fit which means the chassis needs massive effort to rework. So if any one that has suggestions for places that can cut, bend/weld and drill ~4mm Hardox please do share.