Try Youtube..input: 'English Accents'.
Googling 'English accents and dialects' brings up lots of material that you might be interested in but I'm using the UK version of Google.
If you are serious about this, I would first find out how to get the UK version of Google as seen by the British..I think it involves using proxies or something. ..I've never tried or thought of this before so I can't tell you how to do it.
Merged post follows:
Consecutive posts mergedType this in the address bar: http://www.google.co.uk .This should bring up the UK version of Google then click on the radio button that says 'pages from the uk' before you input your search terms for 'English Accents and Dialects'