Class C network models, and quantum and classical delocalisation transitions.
We study the disorder-induced localisation transition in network models that belong to symmetry class C. The model represents quasiparticle dynamics in a gapless spin-singlet superconductor without time-reversal invariance. It is a special feature of network models with this symmetry that the conductance and density of states can be expressed as averages in a classical system of dense, interacting random walks. For a two-dimensional system the random walks are hulls of percolation clusters and their properties are known exactly. For multilayer and three-dimensional systems there are no exact results but the mapping provides a very efficient starting point for simulations. In particular, we present a more precise numerical study of critical behaviour at an Anderson transition than has been possible previously in any context.