Had a play with that and after a few emails back and forth to the owner I had some response from the 2515 Yay!
The next task was to configure the chip to receive messages so after reading the datasheet and the megasquirt can docs 500 times I got a response from the MS2.
After Some more tweeks to the code and plenty of head scratching I set one of my MS2 ecus to can id 1 and connected it to the arduino, switched em both on and hey presto the buffer full led lit up and , some data values were in the serial monitor :)
Now the code is a bit scruffy and getto but its working so far, I need to do some more reading on how to request the rest of the data but its a result.
Few pics of the setup as it is.