Hahah! Well that's an interesting name, it's been a long time since I watched Chitty Chitty Bang Bang. Let's get to these questions:

-Spektrum receivers seem fine, I have an AR610 to go with my DX6i and it seems perfectly adequate. There was a discussion not long ago, have a look: http://www.fightingrobots.co.uk/thre...obotwars-arena

-You don't want pure iron, I think barely anything's made out of iron these days, too heavy and brittle. Hardox (a form of steel used as a wearplate) is commonly used in most robots. It's heavier than plastics or Aluminium, but very very hard. You'll want to keep weight in mind when deciding how much you want on your robot and at what thickness, but quite a few people use Hardox on their featherweights, like Omega, but keep in mind that's a rambot with no weight taken up by a weapon mechanism. Actually, check out Team PP3D's 'Getting Started' guide for a really good rundown of different armour and chassis materials: http://pp3d.weebly.com/getting-started

-Yes Ranglebox's 85A ESCs will do fine for a featherweight, as will drill motors. Just be prepared to find a wheel that'll fit on the 3/8 UNF thread.

-If you can use CAD programs, go for it! I find it helps get a much better visualisation of your robot before you go buying up all the parts you need, or ordering waterjet-cut steel. I used Sketchup, but if you're experienced with more advanced CAD programs like Solidworks or Autodesk, they'll probably help you estimate weight as well, among other things.

-As for general tips, I'd say just make sure you plan stuff out before you buy. The less money you waste on unneeded or incompatible parts, the better. Also personally, I'd advise doing your wiring last. I wired my electronics up before I finished the chassis, and all the moving about has played hell with my soldering. Though I did use quite stiff wire, so that has undoubtedly contributed. I'll be doing a rewire once I'm finished with nice flexible AWG silicone-coated wire. Others will have plenty more tips for you, they'll probably know more than I. :P

Best of luck!