There are detective shows called Endeavour and Lewis running (repeats) in the UK; they're offshoots of the Morse series. They have ad-breaks, i.e. the narrative stops and the show titles appear; but there are no ads. I think that's on ITV. And sometimes there are ads between the titles.
There's something I was watching on Sky, that had ad-breaks, but no ads; instead, they showed a still frame saying that normal content would be resumed shortly.
When they do show ads, they are nearly all:
* Motorised recliner armchairs
* No-medical life insurance
* Home equity release plans
* Charity appeals with fluffy puppies and sobbing grandmas.
That is, the ads mostly seem to be pitched at retired people, and the ad slots are being sold to low-budget advertisers. I use a PVR, so I barely notice ads. Most cable and satellite providers these days provide a PVR as part of the service. So my guess is the TV advertising business model is collapsing; only poor people, and people too demented to learn to use a PVR, actually watch ads.
Meanwhile, running an ad slot with no ads in it must be saying something rather loud to potential advertisers: "We can't sell this ad slot, so lowball your bid!".