If you wanted priority over the Sainsbury's van then you should have already been on the cyclepath, as you were not, then you do not get that priority, you were as other have already advised effectively turning right at a crossroads where the vehicle going straight ahead has priority.
Just an observation on your observation, I have just watched the whole video & apart from a very brief occasional shoulder check at occasional junctions you appear never to take observation looks around to see what other vehicles are around you, you wouldn't last very long on a motorcycle with such lack of observation.
But the succinct answer on this is you are wrong, you do not have priority over the van, he/she did nothing wrong, take it onboard & learn from it.