Undertaking HGV’s a cyclists perspective

So this happened; okay it wasn’t actually an HGV, it was a Bin Van, but either way it was a bloody big lorry. I was on the way to work, it was a cool crisp dry morning. Up ahead was a woman on a bike about 50m ahead, I was catching up to her. As she passed a side street a large council refuse collection vehicle pulled out between up and headed off up the road. Within a couple of seconds I was closing in on it and easing off the match its pace; there was a parked transit van up ahead and little room between it and the Lorry. It wasn’t going very fast following the other cyclist anyway and then slowed and started to indicate left to pull over behind the transit. This wasn’t a turn it was pulling over to collect more bins.
I had come to a stop a few metres behind it, mindful of all those stories of young people being squashed by left hand turners in London. At this point time becomes very elastic; it didn’t take more than two seconds stopped behind the lorry to know he was not going to pull over, just sitting there in the middle of the road, so I gave a forward wave; still no movement, then I wave again and shout ‘Get on with it’ – one of my favourites. Still no movement so with a glance over the shoulder I turn and go right around the outside of the Lorry. He gets the idea and starts to pull over finally. As I start to speed up again I pass the open window of the driver he shouts something, could have been ‘what do you want?’ I shout back (as there no choice but to shout to be heard) ‘You indicated first.’
Now I don’t know if he though I was taking the piss or not, or getting in his way even though he was ahead on the road. What I don’t understand is why he would thing I would happily cycle up the inside of him whilst he was indicating left. He might have stopped but how am I to know he won’t change his mind as soon as I set off? Perhaps he has had many bikers with a death wish undertake him; or perhaps just perhaps he didn’t understand what I was doing or why.
Result is possibly one more driver of a heavy vehicle annoyed with cyclists but I am still alive and lost another 30seconds changing time at work.

Sorry if the title is a bit sensationalist, but an anecdote about NOT undertaking a van that is NOT an HGV wouldn’t scan right. Anyway I hope this is apropos this week.