(at around 43 mins) Neville is looking through the window of the hut wearing a light brown jacket, when the shot moves inside the hut he isn't wearing it any more.
Although Neville only gets his tattoo at the end of the first episode, it can be seen beforehand coming out of the bottom of his shirt sleeve in some scenes. One in which it is particularly noticeable is the scene in the hut in which he and Barry stay in whilst the others are having a night out in the town.
The lads push Oz's Ford Zephyr to "bump" start it even though it is quite clearly an automatic transmission also Neville is able to turn over the engine despite it being seized. A seized motor would just click on the starter, not spin over as depicted.
After Oz's Ford Zephyr breaks down on the autobahn, Neville comments on the bottom of the sump "dropping off". Dennis and Oz walk back around the front of the car and although obscured by the open bonnet, they can be heard talking, and although faintly, snippets of the conversation can be made out. The next shot switches then to Dennis and Oz and their spoken lines sound very much the same as in the previous scene.
It would seem highly unlikely that the Dutch customs officials would not recognize or know what a spirit level was.
Neville Hope's tattoo can be seen (at around 53 mins) seconds but yet his character doesn't get the tattoo until the end of the episode 1.