Managed to get RAID 1 working but the sync process claimed it was going to take a serious amount of time. Looking at the stats revealed that the sync operation was running at a max of 250kB/sec which seems chronically low.
Basic drive performance (hdparm) tests seemed OK so I guess the controller's not up to it?
The info that came with the controller was all-but-non-existent but during a reboot I noticed that it flashed up a 'press CTRL-S to enter RAID setup' for about 1/4 sec and I managed to catch it and define card/BIOS-based RAID but this got confusing because when I restarted the server, Linux could still see 'hda' and 'hdc' rather that a single 'drive' as I expected.
That's where I left it as I had to go sort out a couple of WIN2K servers (mumble mumble) with trojan infections! Next week I might try putting the drives on separate controllers again and re-setup Linux software RAID, otherwise I'll check out some of the recommendations I saw earlier for better controllers.
Thanks
NK