I've already sent off my entry, so don't know where your rogue "I" came from in 15d, but the answer was indeed SLAMMER. Likewise, your "a" at the start of 21d is wrong. Answer is an anagram of "old" and an old word for "the."
It was pedantic, but most don;t realise that the "ye" in "Ye Olde Tea Shoppe" would have been pronounced "the" (though it wouldn't have been called that at the time, tea being a later introduction!)