"I am German, currently living in London(UK) but grew up in South Africa(SA citizen)."
And I thought I had identity issues...
Seriously though, from what you say I would suggest doing the SA com first, building some hours and converting to JAR later. Remember, the hours that you build will always be valid and count for the hours requirement of another licence. If you were desperately keen to get into an airline I would probably suggest going straight for the JAR licence. However, since you are obviously keen to experience some real flying before going this route, I would suggest doing the SA licence first. There are a couple of threads on this forum concerning converting a ICAO licence to JAR.
I think in the long run you are not going to save a huge amount of money doing it this route, and you will have to sit both sets of exams, but you have more chance of building up flying hours that will put you ahead of the pack. You will probably also have some great experiences, meet some interesting people and have a lot more bar stories than if you just go the JAR route.
The flip side is that the European market is a lot healthier now than it has been in a long time. However, competition among low time pilots for airline jobs is as competitive as ever - but then again you don't want to get straight into an airline anyway. You pays your money and takes your chances...
If your intentions is to get the JAR licence in the long term I suggest getting a JAR logbook and logging your time in their format from the start.
As for enqiries to the SA CAA - I always take their answers with a pinch of salt since it depends on who you speak to - some of the people there are clueless. I was recently told that in order to renew my Instructors rating I would have to do a flight test on a retractable VP aircraft, which is completely wrong. Ask for Claudia in FCL as she will most likely give you the most accurate answers.
Good luck!