I haven't read Porn, but here's some ideas of what it MIGHT mean!
Haven't a clue about the stayback
Sovies or more correctly sovvies is short for sovereigns. Sovvies are an old coin, no longer in use, which were gold. It became a fashion a few years back to have them mounted in large, knuckleduster sized rings, or as medalions to wear on a gold chain round the neck. Worn by both men and women. Not very fashionable nowadays - and pretty horrible, even when they WERE fashionable
Saughton's Chosen Few? Well, Saughton is a prison in Edinburgh... presumably a group who met on the inside of its walls?