I went to the garage this morning but they were too busy to fix the fault. However they could spare 5 minutes to look at it to see if it was going to be expensive. It turn out the retaining bits for the rear nearside drum brake had come apart and it was these rattling around in the rear wheel causing all the (LOUD) noises. It honestly sounded like the van was falling to pieces.
They ordered a new retainer kit and will be fitting it tomorrow morning. Due to not being able to drive it today I am behind schedule so won’t make it to the Peterborough show until Friday. I am looking forward to seeing everyone there (If I can find you)