When watching something via On Demand or Catchup does Tivo use one of the 3 Tuners?
For example I was watching a programme from All 4 and at 9pm last night I had three programmes due to record at the same time, when 9pm came Tivo wanted me to stop watching the All 4 programme so it could record the 3 programmes and use the 3 Tuners.
I thought when watching On Demand it used one of the 'player's and not a tuner, not that I am an expert of such things.
BBC Catchup, or indeed any app-based viewing, uses the inbuilt broadband modem. Channel 4 uses the "legacy" VOD method which does indeed use one tuner - so you would either have had the choice of continuing the OD viewing and dropping the lowest-priority recording - or dropping VOD.
Tivo would automatically have rescheduled the cancelled recording, if an alternative showing was available.