Hi, Keilan, welcome to the forums!
It is hard to say, without taking a look to the book itself, but I don't think it will be much of a problem...
If one person is British and talks to an American, an Australian and/or a SouthAfrican, there will differences of accents and common expressions, but I don't think they will have any serious problem to understand each other...
Same with Spanish... I may be surprised listening a Mexican person, or Chilean, Colombian, Argentinean... or Cuban... And they may laugh at my accent and/or expressions, but overall I don't think there is a big issue...