Report of the 'Beyond the Standard Model' working group of the 1999 UK Phenomenology Workshop on Collider Physics (Durham) 1. Introduction by Allanach, B, van der Bij, J, Dedes, A, Djouadi, A, Grosse-Knetter, J, Hetherington, J, Heinemeyer, S, Holt, J, Hutchcroft, D, Kalinowski, J, Kane, G, Kartvelishvili, V, King, S, Lola, S, McNulty, R, Parker, M, Patel, G, Ross, G, Spira, M, Teixeira-Dias, P, Weiglein, G, Wilson, G, Womersley, J, Walker, P, Webber, B