Many thanks for that very useful reply. I was missing the spi-spidev overlay load.
However, I now have another problem (sorry for this). The param_spidev_spi_bus parameter gives the bus that the MCP2515 is on. However, this appears to be the only SPI device that is created, So, for example, if I set it to 0 then I get /dev/spidev0.0 and no other devices. By using the overlays spi0, spi1 and spi2 I was hoping for /dev/spidev0.0, /dev/spidev-0.1, /dev/spidev1.0 and /dev/spidev2.0. Also, shouldn't there be a way to avoid activating the MCP2515.
Once again, many thanks for your help!
Jim.