Your Belgom is a very mild polish mate.
You need something more aggresive, you could try some "00" fine wire wool or Polished Bliss sell all different metal polishes http://www.polishedbliss.co.uk/acata...ts-engine.html

If you give them a call or email them with your pics they will tell you the best course of action.
They are normally pretty good with responding to emails and will help if they can see the problem.

You could also try one of the metal polishing kits off ebay that fit in a basic drill to machine polish it.