No if Shirou uses your era's English most of us won't get it!
Besides, SUBS!
Her era it wasn't even English yet, since the Angles were just starting to migrate in - she's late 5th century, they started migrating in mid 5th century. Unless she knows every minor immigrant language in her kingdom, the language she'd be able to teach is Common Brittonic, ancestor to Welsh, Cornish, and Breton.
well...what Shirou chanted back there i think it was the meaning behind the poem which is his Unlimited Blade works, not the actual poem where he says "I am the bone of my sword" and all that
Shirou...! I can teach you if you're not good at English pronunciation!
