BTW I have already tried to S-OFF (from MCR9 AS2D+, as no other ROMS seem to be stable for me), but when it rebooted after stage 1, it reported no device found, followed by "waiting for bootloader", even though the Desire had now rebooted into bootloader. As nothing further happened (after waiting 10mins), I just gave up, went into recovery and did a Nandroid restore. I suspect the issue there might be that the USB connectivity has to be redone at each stage (reconnected), since the Desire isn't seen, but unplugging during this process is obviously fraught with danger. I had of course installed the HTC Fastboot driver.
Any advice/help appreciated.