This is the longest place name in the UK and while it's not truly translatable, it's often translated as:
"The church of St. Mary in the hollow of the white hazel near a rapid whirlpool and the church of St. Tysilio of the red cave."
However, this translation is a bit of a simplification. The name is actually a combination of several Welsh words and places, and its exact meaning is a bit more complex.
Ultimately, while we can translate the individual words, it's hard to capture the full essence of the name in English.