Deliberate mistake: When the appliance crashes into the drunk driver's car and flips over, water is seen spilling out of the top of the appliance. This appliance was specially designed to flip over by mounting the water tank at the top, to make it unstable enough to tip over.
Episode #4.7 - S4-E7
Factual error: In this episode Blackwall Station is shown as a London Underground tube station. Blackwall Station is a Docklands Light Rail (DLR) station. Also look at the destination sign on the front of the train, which reads 'THAMES LINE', No such line/station exists on the London Underground.