I figured as much. Thank you Michael, much appreciated. I wouldn't mind using the aluminium because A) it gives me a chance to try and do some metalworking, even if it's just aluminium, B) it gives me a reason to use the cans of diet cola and energy drinks I have lying around, and C) if everything goes well, I can just remove, hammer out the kinks and put it back on whilst the batteries charge and the typical damage checks haha.
I mean, you could use the cans in a layered fashion (though it would have to be well layered). However, it is less work to maintain something like Nylon as a skid plate. The Honey Badger has just had a door plate put on the front of it which is made out of Aluminium and it is fairly soft, my metalworking hammer can easily bend it with a single hit but it is supported by the HDPE wedge underneath it so if you wanted to go down that road, that could work.

My questions are... what's the best way of mounting wheels to the drill axle? Is there a better way of cutting out the wheels? Because they need to be at least 12.5 cm to 13 cm in diameter. Or are there wheels that size that I can slip onto the drill without problem?
I'd check out the commercial section as Gary suggested but I took a look at fleabay and maybe something like this if you were going to use a chuck? http://www.ebay.co.uk/itm/M8-Thread-...-/362027342339

The wheels you see on the bot right now is what I cut out of that sheet, as explained a couple of posts/videos, and honestly, the quality of my cutting is absolutely friggin' shocking.
Can't be as bad as mine, one side looks absolutely hacked to ribbons just to get a kinda/sorta reasonable shape on it.