Don't bother looking in England or the UK in general, it's expensive as hell here.
I'm know you didn't ask for that, but you can tick it off your list.

You are right, places near hydro dams do get really cheap electricity, sadly the only friend who could help with quotes in that example, lives in Las vegas and building a mining farm there would be silly. Far too hot, so you'd just end up spending more money on cooling.

I have heard very good rates in a few select places in Europe, Norway especially, it's so cold so they don't really have to worry about cooling and they have hydro dams up there. Could ask a contact out there if you really interested. Only problem is I'm not very fluent in the language.