Men's cowboy boots?

I want to get a pair of men's cowboy boots, but it's difficult because I'm in the UK so hard to find and I don't know what to look out for!

So firstly, where can I find some? Real leather and probably brown, any online places easy for being in the UK?

And next, what are all the size conversions?

And lastly, something I really don't know, what am I looking for? Any real cowboys can help - I don't know what style, how high they should come up the leg, heel size, or anything like that?!

Thanks!