Wheels: I would say use something like Autosmart Smart wheels and Autosmart Tardis, you can use any mild clay to be fair but i would not use it on the paint after you have done wheels.

Interior plastics: i use Poorboys Naterial look dressing but its each to there own really

Engine bay: again is personal choice, i'd try the muc off if you have it already, if not maybe megs super degreser.
To treat with after i have seen good results from 303 Aerospace protectant, have got some but yet to try.

Exterior: Try what you have as there is no point spending just for the sake of it, but as said above i would give the Clearkote red moose glaze then the 476 a go as its a long lasting sealant/wax

I generally perchase my stuff from cleanyourcar.co.uk and polishedbliss.co.uk

Hope this helps