The National Grid Company Plc is responsible for the maintenance of the high voltage electricity transmission network in England and Wales. It must plan maintenance so as to minimize costs taking into account: (1) location and size of demand, (2) generator capacities and availabilities, (3) electricity carrying capacity of the remainder of the network, that part not undergoing maintenance. Previous work showed the combination of a Genetic Algorithm using an order or permutation chromosome combined with hand coded ``Greedy'' Optimizers can readily produce an optimal schedule for a four node test problem. Following this the same GA has been used to find low cost schedules for the South Wales region of the UK high voltage power network. This paper describes the evolution of the best known schedule for the base South Wales problem using Genetic Programming starting from the hand coded heuristics used with the GA.