"
Well, I was walking down the High Road
And this guy stops me
He'd just got in from New Zealand
And he was looking for mushy peas
I said, no, we hadn't really got 'em round here
I said, but
Strummer is saying that he was out walking on "the highroad", which may be literally, meaning he is actually on the high road, or metaphorically speaking, he has reached an enlightened state and is in the position to give great advice and take good advice. In short he is a humble, easy going man that is open to any experiences that will assist in heightening his soul/spirit and mind.
Strummer is also saying he is very welcoming and helpful beyond the literal meaning of those words. He is just not assisting a stranger who is in search of something that he does not have but he is giving this stranger other options that will please the stranger and in hopes, enlighten the stranger as well.