Hi there, I am busy with the JAA exams at the moment, I have looked into the conversion process in depth and let me share the following with you.
If you have 3000hrs command time on a/c over 30Tonnes, then you write Law and Human performance, and you get a license, BUT, it is very restricted. You will be limited to one a/c type, one registration, ie: you will only be able to fly G reg if you did your test in England, and you will struggle to find work, as most companies want a full license with no restrictions. This last info is from friends who went this route.
If you have over 1500 hrs (P2 time counts as half) on multi-crew a/c (Beechcraft 1900 does not count, do not even try tell them it is a 2 crew a/c, they will tell you to go away), you need ATR/ Dash 8 or similar., then you need to sit all 14 exams, NO GROUND SCHOOL NECESSARY. Then you do a flying test! Another costly exercise in itself!
If you don't have the above, then you have to complete a full ground school course, probably in the UK, or similar, at a recognized training center, Bristol ground school or similar, sit the 14 exams (63 GBP each as we speak) get your hrs up to date, and do your flight test too, you will also need to complete a MCC course.
As for SA going the JAA/ EASA route, in my opinion, it will probably be very similar to a European license, but it wont automatically mean you can work in Europe, visas/work permits aside, it is all about protecting Euro jobs, why give SA pilots JAA licenses and let them come work in Europe, when there is no work for the locals. I dont think it will be full JAA license. Maybe similar exams syllabus........but I dont expect the Euro's will let you get a license easily.
There are SA license holders working in Europe at the moment without JAA licenses, they have managed to get validations from certain countries, eg: Ireland, and MUST be P1 rated on a particular a/c, and are restricted to remain at that company on that a/c. This was all when times were good and now that things ain't so good, I don't think this will be happening at all at the moment.
Hope this helps!