Cheers, Fivetide, I followed the tips in your private message and did that. Me and Dave scratching around in the churchyard gravel for perfectly smooth and non-porous pebbles was a new low!
Here is a photo taken into the barrel as we were syphoning the beer into the barrel, with the dry hop bag and syphon tube both visible (we're using the muslin bag you kindly sent us for the other batch we have on the go - a small amount f hops in the mild):
