I think it gets its collision avoidance through a Goodrich Skywatch 497.
This is what I was looking for. The SKY 497 is a dedicated onboard traffic sensor which does not utilize the TIS datalink capability of the Mode S transponder to relay traffic info from the approach radar. The fact that you are seeing traffic targets in the UK with this system does not mean that radars there support the TIS datalink.
2001ft: my best guess is that TIS is US only, and if so, you will need to add a traffic sensor in the acft to see traffic on the 530. In the US TIS capabilities are described in the FAA AIM - possibily there is a similar publication in the UK.