'wax' or 'polish' ???

polish by definition is mildly abrasive - the white shit in Autoglym and the like is chalk. In conjunction wth the solvents, it may well make ya car shine but won't be doing the paint any longterm favours. It's the combination of solvents and chalk that make it 'easy' to use and apparently get it all clean and shiny.

A decent (and therefore not cheap) wax on the other hand forms a protective layer and feeds the paint to replace the oils that are leached out due to weathering and UV (anyone with a 'pink' Ford knows about this effect - once pink you will never get it back to proper red.. )
A decent wax however will contain no cleaning agents, it will go on top of whatever is there and seal it all in nicely - so use a decent cleanser beforehand to get the paint properly clean to start with.

IMO, Waxwizard AKA Swissol, or the proper Zymol (not the Halfords stuff), or Meguirs as a cheaper option.

Cheers
Rich