And that's not even including that Billy appears to have stolen paper evidence from the stash of Eadie Tulloch's papers Sandy was wading through.
Sandy made reference to a couple of things that were missing, and that might shed light on the source of the money -- I assume that's what Billy had snaffled and was putting into his home filing cabinet...?
(And yes, Colin is insufferable. He's insufferability in a waxed jacket. It says a lot for the fact that although we knew the Burnetts were actively engaged in drug muling by that scene where he appears and asks them if they say anything in the graveyard the night before, we still want to say 'Oh, sod off, nosy! Leave them alone!')
I have to say that in Colin's shoes, I would not be wandering out to investigate suspicious nocturnal activity by myself in a hamlet of about six houses that's had a murder and an arson attack within a couple of days, and nor would I be asking aggressively nosy questions of total strangers whose arrival coincided with the muder/arson, and nor would I be poking my nose into their shed and opening mysterious rucksacks with my back to an open door...