Palliser,
the 120k resistor is positioned to the left hand side of the end of bus jumper pins (between the CANL & CANH markings on the Waveshare board).
Thanks very much for your points regarding ultra-low sleep current mode, and the filter & buffer capacitors, i'll defiantly keep it in mind and can see the advantages of the 234 over the 230.
With regards to "pin 8 (Rs) is been underused and fixed to ground (high-speed mode)", looking at the datasheet for the 230 (link below), I don't think that this module / interface board is actually set for full high speed mode, as it has a 10k resistor before the ground connection, and reading the datasheet, this seems to imply that it is actually set up in slope control mode (pg 20 of datasheet) as ~ 15V/usec, does this not imply that it is actually not in full high speed mode? But I may have misunderstood the datasheet (is slew rate not related to the bus frequency?)
Many thanks again,
regards Rob