Thanks for coming back on this
Yes, the car works fine with an "empty" Carloop plugged in but also with an Electron/Photon with only Tinker on it.
I'll have a read thorugh that linked page and come back after some tests.
Yup, Julien, that was it
250000 is liked better by my car (although that Renault list states "Renault Espace 4: 2.0 dCi, Diesel (175HP) 2006 CAN 11bit (500kb)" )
My noobish thought was, since the device is only "listening" but not transmitting, it might just not understand things with the wrong baud rate, so I never thought that could cause the car to play up.
Now I can get on to learn what signals my two ton computer produces and how to use them