Something you want to check is how that 'modulator' box handles HDCP, it is clearly capable of turning an HDMI input into a DVBT output, but will it only work for unprotected content such as the FTA channels or is it also a HDCP stripper. Generally speaking digital to digital HDCP strippers are as I understand it prohibited under the usage terms for the HDCP chips, which is why you don't see HDMI to HDMI HDCP strippers, but maybe as this converts to DVBT that doesn't apply but as it is not mentioned it is something to check before buying.
In the past I have opened sky box connected to caddy or then backed up with this software, image from drive of selected recordings. Then migrated selected from various backups to new drive for new sky box after original sky box failed. Cost me £20 for full version but worth it to save those personally important recordings. Bit of a pain to dis assemble box but once done once, 30 minute job. Ran system once with hard drive caddy permanently attached to box so I could do periodic backups via another caddy.
Final qualification is that I haven't used this software in anger for 18 months and sky do have habit of changing things. Although software has worked with many changes and there is a support forum.
As you would expect will invalidate your sky box warrantee. But sky's approach to failure is swap box so you lose everything!
Thanks for the replies, I think I'm going to have to take the plunge and get myself an Edision modulator and find out for myself, if not I'll still have SkyHD all around the house, bit better than the old analogue picture.
I don't know about a pc based recorder, but you can certainly record the output from a sky box modulated with an edision to a usb stick using my old samsung 6000 series smart tv. As far as its concerned itsjust anotherfreeview hd channel.