The Hyper 7 is very popular because of it's reliability. I would get whichever is the current version, which it the Hyper 7 TQ Black Edition I think. I don't know where they come up with these names I am also a big fan of getting a car that has good local parts support. Or at the very least, make sure that you can get parts easily online. I'm not familair with UK hobby outlets, so I'm no help there.

Don't worry about upgrades until something breaks. The dogbones shouldn't be much of a problem. Don't upgrade the suspension arms to aluminum. You'll just start bending/breaking hingepins or the hingepin blocks. The plastic is plenty strong and very resiliant to impacts.