Considering the era they were made in, that's not suprising.
I'm sure when CITV broadcast an 80s episode as part of their 30th birthday weekend, it ended with a Fremantle ident, I could be wrong though. Weren't the DVDs of it released by Pearson/Fremantle too, or have I got that wrong? I know at the very least some episodes got released on compilations alongside Rainbow and Cosgrove Hall stuff, which was obviously also Thames.
I have one of the DVDs somewhere and it was released by PT Video, which was the name used after Thames Video (post VCI split) and FremantleMedia for their releases. The DVD does even have the Thames skyline ident at the start of the first episode on the disc.