Some more persistent searching seems to have cleared things up.
The Philips rc026 changer has an analogue output, as indicated in the last post on this French forum (google translated)
Both the French forum and the very useful list on the TLCDC emu faq agree that the DC259 has a spdif input. The TLCDC faq also suggests that the analogue and digital head units don't use the same protocol, hence the tuner list unit not detecting the changer. ( http://tlcdcemu.sourceforge.net/faq.html
It appears that Renault started supplying tuner list head units instead of sat6000 units part way through '99. Which is why my initial googling seemed to say that the two should be compatible.
For any one thats interested I found a pinout for connecting a digital changer to tunerlist head units on another french page, google does a good job translating, but you only really need the pictures.
There is a very short list of cd changer compatibility for different years:
I suppose you can add the french guys VDO CHD602S as compatible with tunerlist too.