I use Autosol metal polish on my exhaust and it always comes up a treat. You can get it in a tube or a bigger tin from motor factors. About six quid last time I bought some though that was a while ago - it lasts forever.
Im going to have a go with some liquid Brasso I've got, it should be okay fro the window frames, but not sure about s/steel. If no good then I will try Windowlene.... can you still buy it?
I've used 'Brillant' Metal polish which I got from The Polishing Company, seemed to do the job. The Leven fuel/oil caps polished up a treat, but the window frames were only OK at best.