The same green, navy and burgundy knitted tie makes at least four appearances throughout the series. Worn by at Laurence Fox, Alan Davies, Christopher Bowen and David Calder. There is no reason in the story line given, clearly someone in the costume department thought it deserved screen time.
In her initial observation of the dead man on the bus, Laura (the pathologist) comments that he was "overweight". It is later made clear that the body was moved in the back of a vehicle, but not how it somehow managed to then get all the way up onto the top deck of a bus, especially as the eventual culprit turned out to be a person of very slight build.