Well, it's by the same guy who did last years execrable 'Kill The Moon', so I wasn't expecting much, though I hoped to be proven wrong. No such luck.
Clearly UNIT has suffered major budget cuts, relocating from the Tower Of London to that grotty house. There are now so few troopers that killing a dozen of them plus Jac the HQ staff is apparently enough to completely 'neutralize' UNIT UK. And it seems they only have one drone operator, otherwise the one who refused to fire would have been relieved of duty and replaced. And wasn't it odd how she just happened to zoom in on the one part of the village that had Zygons impersonating her husband and son standing out in the open?
The UNIT personnel who were present seemed somewhat less competent than you'd hope for in an elite alien defence organisation. Even knowing they were up against shape shifters, there was no real attempt to adapt their tactics. The Zygons disguised themselves to fool the drone pilot, and then pulled the same move on the troops, who fell for it. How hard is it to double check the location of your family?
"No ma'am. I shall not fire. My husband and son are there."
"Hmm. They're probably just Zygon duplicates. Still, let's make sure. Put the drone on auto pilot, phone your family, see where they are."
Two minutes later.
"Ma'am, I've talked to my husband. He and junior are at home. Carrying out attack run now."
And as for the troops outside the church, either contact your loved ones as above, or, if that's completely impossible for some reason, send just a couple inside. But keep in constant radio contact! Don't stop talking. Don't give the Zygons time to kill and replace you without leaving a lull in the conversation. And maybe, if the budget can stand it, get some helmet cameras so people outside can see what is going on.
Still, the new, on the cheap, UNIT probably can't afford cameras. They apparently can't afford ammunition (the troops under Clara's flat were killed without firing a shot, even though they realized it was an ambush), extra staff (Zy-Clara was able to swan into the safehouse unchallenged), or, indeed, locks (Zy-Clara was able to get a surface to air missile launcher with no trouble).
On another note, I do hope they resolve the matter of which Osgood this is. I can see them pulling a variant on the 'The Also People', saying that as long as she has Osgood's memories, she has as much right to be Osgood as anyone else. That may be so, but it ignores the fact that those fans who want Osgood back do in fact want Osgood back. Not a copy, the original.
Furthermore, if the situation is left unresolved, and the character used again, the writers would be unable to place her in situations where being a shape shifter with the ability to stun or kill with a blast of energy is an advantage. Because what she does in those situations would rather give the game away.
And if the contents of Osgood's box (ahem) are anything other than the Zygon killing gas so casually mentioned, I shall be very surprised.