Okay, I just finished watching the whole series. And I kind of wish I hadn't. There was a while, a few episodes in, when it looked promising and I was invested in the characters and the world, but as it went on, there were just so many bad and silly episodes, and it became increasingly obvious how incredibly cheap the show must've been. I mean, most of the "adventures" took place either in the mansion or in the sewer tunnels, the supposedly all-powerful Department had only two employees at a time (other than the unseen Lomax), and those employees did most of their work out of the back of a van (which was invisible from the outside so they didn't have to spend money building it). And the cast was for the most part pretty bland, though they made a wise decision ditching the mediocre actor playing Inspector Drake and replacing him with the far more menacing Thorne.
And a lot of the backstory and worldbuilding was so nebulous and so cursorily handed out. It took half the season to learn there'd been a Great Cataclysm that reshaped the world into what it was by 2050 (even though London looked unchanged from 2010), we only rarely got any mention of Lomax leading the Department, and so on. And once they dumped Drake for Thorne, they didn't even spend any time establishing any antagonism between Thorne and the kids before we saw them breaking into his office to gather dirt. It was very awkwardly put together.
Also -- why the hell was everyone white? As far as I can tell, there was only one nonwhite speaking character in the whole 26 episodes, the schoolgirl Vibeka in "Sirens of Ceres." Which just isn't realistic for a show that was meant to be set in London, whose population is over 40 percent nonwhite or mixed-race. And the show was shot in Brisbane, which has relatively large Asian, South Asian, and Pacific Islander populations. It shouldn't have been hard for them to assemble a more diverse cast. So why didn't they?
The main reason I stuck with it all the way through is because I'd recorded the whole thing and I figured I shouldn't let that go to waste. But I can't say I'd recommend it. Which is too bad, because I've always liked K9 despite the silliness (and dog-ness) of the concept.