So there are 4 quarts as well as 3 liters to a gallon. There is around 120ml to a half cup(that should help you calculate down and up from there). As for availability, everything I got for my mix I got from Amazon, are the UK offerings on Amazon significantly different? I'm sorry my country uses such a shitty measuring system, once I learned there were UK members I immediately switched to using either both IMP/MET or just metric. I've been a big proponent of switching, our White House petition got shot down :\ I'd like to buy the world a 591ml Coke :-D
EDIT:> A basic version of the recipe.
30 liters potting soil
3-6 lbs worm castings
283 grams steamed bone meal
283 grams bat guano
283 grams blood meal
170 grams rock phosphate
22.5 ml epsom salt
15 ml dolomite lime
15 ml Azomite
15 ml humic acid