I remember watching this cartoon when it came out in the US during the heyday of the “British invasion.” It had mediocre animation for its time. I suspect that it was simply rushed through to make use of the hype of the band during this time frame. The stories were mostly stupid situations that one or more of the band members got involved in, and the rest of the band were needed to get them out of the situation. The accents used for the Beatles were simply horrendous – I suppose that the voices were stereotypical British lower-class voices that didn’t sound like any of the band members did in their interviews.
At this point in time, this series would be really dated. Unless you are a die-hard Beatles fan, I would suggest staying away from this and go and watch A Hard Days Night or Yellow Submarine instead.