There has been some talk about planned power cuts this winter. From an article on Yahoo News I linked to this document that appears to define the various levels of rota cuts that might be imposed, and the blocks that the cuts apply to, designated by letters A, B, C, D, E, G, H, J, K, L, M, N, P, Q, R, S, T or U. It is said that a letter on your electricity bill indicates which block you are in, although I cannot find it on my bills.
David