I am a great fan of the Longman Pronunciation Dictionary, by J.C.Wells, professor of phonetics at University College, London. It covers British and American pronunciation, sometimes has little statistical surveys, and of course contains all kinds of last names, place names and so on.
The website of the UCL Phonetics & Linguistics Department came up in one of my Jamie Oliver. It’s worth looking at, especially for the Resources and Tools. Here’s some information on Estuary English. Excellent links on estuary and Cockney, including an article in the Süddeutsche (in German). This is a nice warning:
bq. Do not be misled by the title of the work Shallow-Water Dictionary; A Grounding In Estuary English, by Stilgoe, John R., Paperback – 48 pages (August 1994) Princeton Architectural Press; ISBN: 1568980299. The blurb reads: “Stilgoe’s definitions are lyric explanations of the vernacular language of America’s nearly extinct shallow-water regions.” A blow for Rosewarne’s London-centred view of the universe.
As Paul Thomas pointed out in the comments to the Jamie Oliver entry, you can translate a website into Cockney (inter alia) online.