Nait XS with Humax Foxsat HDR

Hi all, I have a Nait XS and want to use the remote from my Humax Foxsat HDR to control source selection (to switch between HDD and AV) and volume. Humax don't list a remote code for Naim. From what I understand the supplied Narcom 4 is a Phillips based remote, and although using a Phillips code does give me control of volume, it doesn't allow source selection.

Has anyone cracked this?

Regards

Will