I wrote...
static const struct cnl_mb_cfg memcfg = { … };
Having been back and verified against the schematics, I have found a couple of value that were incorrect.
spd[1] and spd[3] needed to the set to NOT_EXISTING and the designed is not interleaved so .dq_pins_interleaved needed to be set to 0 not 1.
The board is now booting to a point where the last debug messages are:
enter handle_19: Booting from Hard Disk... Booting from 0000:7c00 NULL
Thanks both for your help in getting to this point!
Next challenge is to sort out the VGA initialisation so that I can get something onto the screen!
-Andy.