Tvheadend

Check Tvheadend's logs. It should indicate which tuner was tuning the program at the time the recording started.

I can't see it in the recorded log, presuming it must be in a general log, do you know where this would be stored on Ubuntu? will it be in /var/log/syslog or is there a cleaner location for it?

Use journalctl:
$ journalctl -u tvheadend

You can also limit the initial display of logs based upon times. Check the man pages for journalctl.