Does your postcode begin with any of the following?
N1, N1C, N4, N5, N6, N7, N8, N10, N15, N16, N19
NW1, NW3, NW5
WC1A, WC1B, WC1E, WC1H, WC1N, WC1R, WC1V, WC1X, WC2A, WC2B, WC2E, WC2H, WC2N, WC2R
W1B, W1C, W1D, W1F, W1G, W1H, W1J, W1K, W1S, W1T, W1U, W1W, W2
EC1A, EC1M, EC1N, EC1P, EC1R, EC1V, EC1Y, EC2A, EC2M, EC2N, EC2P, EC2R, EC2V, EC2Y, EC3A, EC3M, EC3N, EC3P, EC3R, EC3V, EC4A, EC4M, EC4N, EC4P, EC4R, EC4V, EC4Y