Again, I really enjoyed this episode (normally I'm a "Miranda-Sceptic").But: they really shouldn't do these musical endings if it's not absolutely "necessary". Second, they could have worked in Barlow's appearance a bit more plausible. It felt a bit like the situation in Extras/When The Whistle Blows with the guest appearance by Chris Martin in WTWB. Andy Millman was annoyed and said something like: "Don't put in a guest star only because he's available; it's not plausible for a pop star to pop in a factory during weekdays".
Here it was similar: "Hey, it's Take That's Gary Barlow" as if they wanted to make sure that even the near-sighted ones of the audience get it.
I realise they play a bit with the "cheapness"-factor (like Freddie Mercury often did during his lifetime)...but I think yesterday's ending looked cheap because that's what it was; not because it was a kind of knowing allusion.
Keyword allusion: I liked the bit when Miranda said something like "Oh no, I have to begin acting now".