Other mistake: Mr. Smith scans the Mona Lisa and determines that it is genuine from DaVinci's brush strokes. He should have also noticed the words "This is a fake" written in felt tip under the paint, from when The Doctor replaced the Mona Lisa with one of DaVinci's "forgeries" in "City of Death."
Plot hole: When Maria Jackson is running away from the alien creature, she turns left into a metal fencing. The camera shows this seconds before she runs into it, banging on it in frustration. This does not make any sense. She saw the metal fencing, so why did she continue to run into it? Why did she not turn right instead and along the park?