Hello @Joe21, welcome to Sonos Community!
I am sorry to hear you are having trouble controlling your Sonos Home Theatre with the Sky Glass TV remote controller.
Since you’ve connected your Sonos with a HDMI to your TV, the remote controller should automatically work.
First thing to try would be to initiate a Remote Control Setup via the Sonos App. You can find that under Settings → System → “Name of your Home Theatre Room" → Remote Control Setup.
If that doesn’t work then follow the same process as above but instead of tapping Remote Control Setup, tap TV Setup.
I am sharing below two very helpful Support Articles for some additional information and instructions:
Control Sonos home theater with your TV remote
TV remote not detected by Sonos
If none of the above resolves your issue, I would suggest reaching out to our Support Team for some live troubleshooting.
I hope this helps.