Museum curator: "For the love of Darwin, it's a 15-metre tall tree! It's been stolen!"
If the series has been getting a bit more Doctor Who-ish of late, then this episode is definitely a lot more like The Sarah Jane Adventures.
(please God don't let it ever become like the other one)
It's easy to suppose that 'The London Museum' in SE14 is related to the arty one featured several times in that other children's series of late. When K9 discusses ways to sneak in past the cordons to get another sample of the alien goo left behind after a top exhibit's theft, well, it even feels like the same show.
I found the eventual solution to the mystery to be both a cliché, and also visually very well realised. After the people-in-costume aliens of previous episodes, the centuripede looks truly otherworldly, if anything reminiscent of the ectoslime from The Iron Legion comic strip.
As for K9 remembering having met Robin Hood in a previous life, I guess that's just a lucky fragment of his memory. He does seem a tad absent-minded.
K9: "I'm detecting abnormal levels of magnetic interference. Oh, and Jorjie's mother."