Ah, fantastic - thanks for the help, everyone!
I still need to figure out what I'm getting on the electronics side of things, then I'll have a look at the budget (about £100) and see what I've got to work with for wheels - ideally, cheapest is best, but I do like the look of those banebots ones, especially if they're that grippy. I'm wanting something that has a lot of power motor wise, and then can actually lay that power down so obviously wheels are something I really want to get right! Also, in terms of the robot itself, I'm going to leave HardWired I be, and make a completely new HardWired II, similar design but I need better armour and just a general improvement over the old design to incorporate this lifter, so I might as well with how much I'm planning to change.

And finally, I'm looking at getting a fast brushless motor/esc setup on the cheap just for a slight experiment with the old HardWired, and potential weapon system on the new one, so that should be fun.