1 and 1/2 feet sounds like a good dosage, with a diameter of about 2.5 inches. Peyote is legal in the UK, you should buy enough to trip and plant the cuttings, or if they come bare root, jus cut em off leaving a lil cactus stump, prepare the shit u jus cut off, and spray the cactus stump with anti-fungal solution, keep spraying for about a week, or until it callouses over, this stump will in a few months, dependin on where u liv and the season, sprout a sidearm out, which will grow and should be ready to harvest again within a year or 2, peruvians are more resilient to cold climates than san pedro, thats pretty much the only difference, which is why the difference in potencies is noted, the hardier the cactus the more alkaloids. Grown in indoor conditions they'll come out to be about the same, shame you can't jus get sum buttons, easier to ingest (jus eat the fuckers!), more potent, and you don't really av to bother with the lengthy boiling of that of the columnar kind.
Peyote made you think ure genitals had fallen off and were chasing u around? Are you joking?