Standard Accent in UK and US

Hi,

I am just curious which part(London, LA, ect.) of the people speak a standard English both in UK and

US. I am not talking about which one is good or bad; all accent is good I think. What I mean is

that there are quite a lot of accents and dialects from different provinces in my country, and it is stated

in the law that the accent(language) spoken in the Capital is the standard Accent. So I guess other

countries also have a simillar thing. Or, if they don't, which part of the accent is most spoken then?

Thanks.