Hi Tom,
Those motors are only 1.5-3v, not really good enough for our use. A couple of us, myself and Dave Weston used the 12-24v versions of those motors and found them really quite lacking. Changed up to these which seem very popular with Australians and US Builders. I like em too. http://www.ebay.co.uk/itm/2-x-12V-DC...item4d02562621

That esc will work, but I don't much like them, just preference. Many use them to great effect. There are cheaper alternatives if you are interested. Won't be quite as plug and play as the sabertooth.

Aluminium could work, depending on thickness and grade.

3 channel.. do you mean a minimum of 3 channels, or like a pistol grip type transmitter or just stick radio with 3 channels?

Either way, hobbyking and giantshark have cheap 2.4ghz radios, although I think its a good idea to get a fairly decent radio from the off.

Look at 2-4 cell lithium polymer batteries I'd say.

Cheers. Harry.