Shortly after 32 minutes, Sasha asks "From who?" rather than "From whom?". Proof reading and sub-editing should catch basic grammatical errors not in keeping with the character.
This may, however, be a deliberate error, as previously Sasha has used incorrect grammar, such as "should of'"instead of "should have" or "should've".
When Danny and Steve rearrange the film clips in the order the river flows, they put the St. Pancras/Bagnigge clip first. However, these locations are about halfway down the river. Also seen earlier is a shot of some ponds, the only possible location for such ponds is near the source of the river, so a clip including them should be before Pancras.
At about 41:46, just after Denis Lawson sits on a couch to look at his laptop, a boom mic drops well into view from the upper right.