You're the bloke in front of a line of 50 cars and vans all of whom have jobs to do, families to visit, work to get to. The maximum speed of a major road is 60mph for a good reason.
45/50mph is fine for a road with a 50mph limit but not for a major road.
Sorry - I drive and cycle but there's nothing worse than some old codger driving selfishly at such a speed.
Where possible and safe to do so, I'll happily and easily overtake a van doing 45-50 on a NSL road.
Where possible and safe to do so, I'll happily and carefully overtake a van with a car (or two) stuck behind it on a NSL road. There are fewer opportunities to do so though.
Where possible and safe to do so, I'll happily and easily overtake three cars one by one, followed by the van.
What I can't do (on most roads) is overtake three or more cars, driving with no gap allowing someone else to overtake them, behind a van doing 45-50, all ignoring/not seeing/refusing/too worried to take the opportunities that are available to them.
To sum up, I'd never blame the van.