Use American English, I mean general American English. There are too many varieties of accents, and vocabulary, in England, so much so that people learning English around the world wouldn't understand most of them. Cockney, Georgie, Scottish, Irish, etc. Those accents are not popular.
The USA has spread its accent through movies, TV shows, lectures, etc., so all over the world people understand it, but people do not understand most British accents. I should know, I do movie subtitles, we have to pay extra if a movie has no script and it's not American English. We may pay double or triple the amount if the movie is British because it is hard to find someone who can understand the accent(s).
To sum it up, go with what most of the world are used to. Of course, this is the opinion of someone who has to hire translators, so I can say that the only British variety that is cheaper to translate is RP, as it is taught everywhere, the other varieties are too expensive for my taste.