The original poster on this thread raises a very interesting question, which I have come across quite a few times now.
The C525 is certified in Europe as a single pilot aircraft (SPA). When I did my European rating in the 525, the only way you could get the 525 on your licence was (just like any other single pilot rating) to do all the flying yourself, from the left seat. There is no such thing as a "co-pilot rating" on the C525 on a JAA licence. (This is different in the USA, where you can get a C525 rating that requires you to have another pilot in the cockpit with you; in FAA terms the C525 can be operated by two pilots, neither of whom holds the single pilot C525S rating. That is not possible on a European licence - in Europe the PIC must hold the single pilot rating).
Since then I have heard several stories of people in Europe paying for a 525 rating course, and then (1) sitting in the RIGHT seat during the check ride, and (2) ending up with what they believe to be a "co pilot" licence. I am quite concerned about this.
Don't get confused with the fact that for commercial transport operations in Europe the operating rules say you need to have two rated pilots on board - that's purely a safety/redundancy issue. It is still a single pilot aircraft. There is no such thing as a "co-pilot" licence for the 525. (The effect for commercial ops is that both the pilots in the flight deck have to hold the single-pilot rating, but because they are doing multi-crew commercial ops, they are also supposed to hold the MCC rating).
It is possible for you to have some other restriction on your licence that stops you acting as the single pilot-in-command. Perhaps that is what you have - you've got the C525 on your licence (which is a single pilot rating), with a medical restriction that says you need another rated pilot on the flight deck.
Trim Stab hazards a guess that perhaps you don't have an appropriate instrument rating - which would be IR/SPA/ME. That would also be a barrier to practical operations, but to be pedantic, would not stop you flying your C525 sinlge pilot on a VFR trip.
But outside those example restrictions the C525 is a single pilot aircraft, so there's ONLY a single pilot rating in Europe, and there's no such thing as a JAA C525 co-pilot rating.
Which raises the interesting question: All those of you out there who were sold a co-pilot rating - and perhaps have managed to get someone to issue you with that written on a licence - I would be very interested to know (a) who sold you that; and (b) what does it REALLY say on your actual licence?