[James2001]

Yep, that's the one I'm talking about. I remember there being a lot of attention to Stuart Miles and Katy Hill appearing as themselves on one episode- it was still being repeated a decade later long after they were gone from Blue Peter and it must have baffled kids by then. The whole thing has come out on DVD and is in Amazon Prime, so it's not vanished entirely.

It looks like TCC actually aired a bizarre puppet version in the early 90s as well, there's some videos on YouTube.

The 2009 version had some quite awful character redesigns that carried over to the comic, but I don't think lasted long before reverting, and the CGI cartoon... when I first saw a poster for it in the muesum in Dundee it took a while to realise it was meant to be Dennis, god knows what the cartoon is like, but the character designs are awful.