Parts have arrived (the MCP2515 module took a while from China, my local supplier eventually admitted they didn't have stock a week after I placed my order).

It's all wired up with jumpers, ready to start work on the software.

I'm trying the SparkFun CAN-bus library to start with, but I'm not using a standard Arduino, or their shield, so I had to write some #defines to re-map the pins.

// Pro Micro pin adjustments (dunno what to do with the LED...)
// to work with SparkFun library
#define MCP2515_CS    A,7
#define MCP2515_INT   A,6
#define LED2_HIGH     A,10
#define LED2_LOW      A,10

Next steps:

Scope on the CAN output to see if anything is happening

Wire up to my car to see if it can read anything