Well I've been enjoying Flux up to now, but this was a huge disappointment. Division was brought up this season, really built up in the previous few episodes, and all we see of it is an Ood and Tectuan. The Doctor swears to stop her adoptive mother - interesting plot point, can she go through with it? Doesn't need to as Swarm pops in to absolve her of any guilt she'll feel after whatever dire fate she had in store for her.
The 1904 stuff felt tacked on, we get an explanation for the tunnels, but not why the Victorian guy knew to build them. The mystic sketch went on too long. Humour is not Chibnall's strong suit, especially when he drags a joke on.
Then it turns out the Grand Serpent's master plan was to build up UNIT so he could... Cut its funding down the line? What? Here's a thought, if the idea is to neutralize UNIT, why not go back in time and murder the hell out of everyone who wanted it? It feels like a hasty retcon of the unpopular decision to cut UNIT for a political joke.
And suddenly Sontarans! And if the next week trailer is anything to go by, in addition to finally dealing with Swarm we have Sontarans, Daleks and Cybermen added to the mix as well. I really hope the Daleks and Cybermen are going to be background noise like they were in episode 3, or we are looking at an almighty cluster-mess of a finale.
The Ravagers are still cool villains though.