When Gwen and Jack goes into the room in the house, it is a brown wooden door with no windows that she opens, but once inside, it is a white door with glass windows.
The police cars shown in this episode only say "police" on them in English. However, as Wales is a dual-language country, emergency services use both English and Welsh on their vehicles. Therefore, they should read "Police/Heddlu".
In the final part of the chase through the woods, when Toshiko falls to the ground, it's obvious she's falling onto some sort of prepared surface covered with leaves (most likely a mat).