I think, whether we choose to call them “captions and music”, “break fillers”, “interval slides” or whatever, everyone is aware of what we are talking about. I wonder what the internal name for them was within Channel 4.
As the example Steve has linked to suggests, many of them - even from the very early days - were more than just a caption or slide with text superimposed. There were several that were films, such as Christmassy scenes, water birds, driver’s cab views, and helicopter footage of London. There were moving graphics with the “4” symbol, or parts of it, flying round the screen making various patterns - even pages from 4-Tel advertising upcoming programmes.
Rather than the opposite, as time went by the captions became less animated, but some interesting graphics were still being produced and used right up to the end of 1992 - sometimes in the style of the current C4 promo package with the “keep an eye on 4” tagline included on the slides in the early 90s. They did tend to appear less and less over time, but there are numerous examples on YouTube of commercial-free breaks, the latest one I’ve seen dating from late December 1992.
They rarely appeared on Thames/LWT, YTV and possibly never appeared on TVS. They came and went on Tyne Tees until the end of 1984 - sometimes there would be a few months of little or no ads off-peak, then for a while every break was filled, then back to part-filled breaks. Over the Christmas period ads seemed to be scarce, especially when popular shows were being shown on ITV. I think the break captions were quite a regular sight in smaller regions like Border and UTV, right up until 1992, and they lingered around for quite a while on TSW.
I’d be surprised if TV Times promotions couldn’t be used to fill up breaks - often the proper “adverts” for TV Times would be seen on C4 in a break otherwise comprising only PIFs. LWT sometimes inserted a “slide and voice” ad for the magazine at the end of breaks - perhaps even voiced live. LWT inserted live continuity onto C4 for a while and had a dedicated booth and announcer to do so - C4 apparently weren’t too happy that regions like Thames and LWT were opting out of their continuity links and using their own announcers to cross-promote local programmes! AFAIK only the two London stations did this - Thames playing pre-records and LWT voicing them live, but legally any station could have done so had they so wished.
Cut out the coupon in your TV Times!