Living in ireland won't make the parts more difficult to source. Most will be found on this site. Or you just ask individual roboteers by PM.
P&P. Can't be more expensive than in Belgium. And I survive that for about 17 years now, robot wars related stuff that is.

As Runsler mentions, the torque on the axles with wheels that big is huge.
Gabriel and compatriots solve that by mounting the wheels on very very strong shafts, and use drive setups that aim for a reasonably low top speed. Also a huge improvement on controlability .


But, looking at your design, you're building Wheely Big Cheese with wheels on steroids.