Lost Property is very much just setup for the rest of the arc, but it does a great job of it.

Even as someone who's barely listened to barely any 8th Doctor stories, this does a great job of bringing you into the world and the characters. Liv and Helen are immediately likable and all the context you need for their characters is here in this story, and is communicated to the audience in a way that doesn't feel expositionary, Liv namedropping Kalador and Helen mentioning about how much everything's changed could have ruined the pacing or feel forced, but they really don't with the way that they're done.

I also like how little we get of Eight here, this isn't a situation he's used to at all and more than anything it just frustrates him, drawing on the characterisation of Eleven in The Power of Three or Three in most of his era, and unlike those two he doesn't even have alien threats to figure out. He sort of isolates himself in a way that makes a lot of sense until he's drawn out at the end by Liv and Helen. In perfect contrast to this we also see The Curator, this future doctor who doesn't want to meddle in his own timeline but knows he has to do something, he's so charming and personable, and it's a great reminder that The Doctor can be that, he just needs to try, so when Eight does at the end of the story, it works really nicely.

The will-they-won't-they dynamic that the new character of Tania introduces for Liv is great as well, and especially knowing a little more about her character, I can't wait to see more of Tania going forward.

The actual alien threat in the story feels a little underdeveloped unfortunately, but it's not trying to be a big part of the story and I think it works for what it is.