Revealing Mistake: When Tilda throws the knife at Pex, the string holding it can be seen.
Revealing Mistake: The lift apparently has only one door, not the double door that would be needed to prevent anyone from falling into the lift-shaft.
Continuity: Pex and Mel leave Tilda and Tabby's apartment on floor 109 to get to the pool. When they catch a lift, however, it is on floor 48. It's unlikely they climbed 60 floors down in their attempt to reach the top floor.
Revealing Mistake: When Tilda throws the knife at Pex, the string holding it is visible.
The Doctor [ taking the Paradise Towers Prospectus ]: I'm sure there are some rules to govern this, Deputy Chief.
Deputy: [Mumbles through his gag]
The Doctor: That's the most intelligent thing he's said so far.
Chief Caretaker: I think it would be good idea if before your death you and I had a nice little Regulation 13 Appendix 2 Fine Conversation.