First of all, with this post, I don't want to sound like a know-it-all; I'm far from it. I can only repeat what I learn from instructors.
Sorry, I have never heard of Northern Soul Dancing.
However, I took a 8-week workshop on spins and turns. It was quite an eye-opener for me. A "spiral" is actually a type of turn, not a spin, and I have only seen them done in the latin dances. A spiral is actually a 3/4 single turn, done so that one leg "wraps" around the other (kind of what the colors of a candy cane look like), giving the effect of a "spiral." The spin you're refering to, several spins on the spot, is a whole different game. Although this type of spin was part of the workshop agenda, its name eludes me. During the workshop, we started out with one spin, then tried two spins. The instructor did challenge us to try a triple (haha on me). Like UlfChild said - a little bit at a time.
Something else that will help you with spins: Learn how to spot and practice it throughout your dancing, not just for spins. In any case, spotting greatly neutralizes your equilibrium. Start out slow in practice.
Regards, Hoofer