That mix looks brilliant, What seed rate and cost of seed for the grasses and hemp? Also what's the benefit of hemp please?
The mix I used was actually bird seed. So no choice in the mix. It went in at 14kg/ac as I guessed the rate. In reality it could be halved at the very least, probably sown at 4-5kg/ac. The stubble turnips and clover were at 5kg/ha.
The bird seed was £1/kg, but you could possibly make the mix yourself a lot cheaper, especially as the bird mix had a lot of sunflowers, but a lot were eaten by birds.
Hemp doesn't seem awfully palatable, but it does get trampled in and provides some ground cover, and there is a reasonably extensive root system. Linseed is similar. It does provide some novelty factor though, and the local soil science students eyes lit up when they saw it!