I think I may have found a way for you do do this without the need of a computer as the server. Hopefully you should be able to setup the sat box as the server.
Install the plugin 'dlna server' on your sat box. Hopefully this should allow the sat box to be seen on the network as a server. You then need a client on the now TV box. Playto seems to be compatible and from what I've read can be installed onto the now TV.
This should then allow you to stream from the sat box to the now TV. However, I think it may only allow you to stream your recordings. In this case you would need to create a folder on the hdd of the sat box and place all of the m3u files in that I mentioned earlier. You should then be able to play these files, which will open the streams.
An an alternative to creating the m3u files is a plugin called mediatomb, but I think it is no longer developed and therefore not sure if it still works.
Either way, I'm sure this is possible, but might take some reading and tinkering to get it to work. Let us know how you get on.
edit: before you go to all this trouble, just to warn you I'm not 100% sure that playto can act as a dlna client. If you can find a dlna client for the now TV, then this method should work (at the moment I'm struggling to find one). If not, you'll have to go the plex route.
edit2: if it is a smart TV that you're trying to stream to, then most likely it will have dlna connectivity without the need for the now TV box.