Steve...It's easy for us all to second guess after the event mate.
If there was enough room and sufficient time I might have been tempted to drop a gear and accelerate past the van. He would then have had absolutely no mistake at what he had almost just done.
Slamming on behind him meant you had to go through a severe sphincter test that he was totally oblivious to.
If not enough room and time then a controlled slow down using both brakes and gear box.
Not something you should be beating yourself up about though mate. Glad you survived it without too much grief.
