I have owned the mini im driving at the moment for a year but my previous mini was owned from the start of production.
As for bird droppings yes it will discolour the paint but the process i mentioned earlier will remove this, that is unless you leave bird droppings on your paintwork for quite a few days.
The chips issue wasnt raised earlier and i agree with you on this, but the question was about restoring the paintwork back to its original shine and depth.
Unfortunately bird droppings and the like are now much more toxic due to the polluted and insecticide world we are now in.
The polishing process i described earlier will remove a lot of blemishes , swirl marks and discolouration from paint.