I'm looking for a bootloader that supports the MIPs architecture and
HDD support. If anyone knows of such a bootloader (GPL or otherwise)
I'd be very grateful to hear of it.

The system I am building will have a bootloader that resides in flash
memory. When the system powers on and runs the bootloader (out of
flash) it will uncompress and initialise the kernel and the resulting
apps, all of which reside on a HDD.

The obvious choices like GRUB and Lilo don't support MIPs. All the
others I can find that do support MIPs don't have HDD support.