Better than a lot of Japanese singers I've heard!
Here are my comments. Note that I'm by no means trained in English teaching, so take my comments with a grain of salt. Also, I've been trained with an American ear, not British or Australian, so I might have some inadvertent biases towards how some things should sound.
1st speaker
Well, he hesitated a lot before each sentence, but I do that sometimes too, and he got better with eliminating the "Ah"s as he got more into the exercise.
The "these" of "ask her to bring these things" was a bit on the "breathy" and nasal side, and needed a little bit more "hardening," which can probably be corrected by biting down on the tongue just a tiny little more and speaking not from the top of the throat.
The "her" was too close to Japanese phonetics, sounding more like "Haa" than "her". Make him raise the tongue up a little more.
snow peas - snow kept sounding like small, if I hadn't looked at the words. The o should not be like the o in orange, but the o in boat.
"Five thick slabs" - again, the "th" sound was not hard enough, sounding almost like an "s" sound. I know Japanese interchange "th" for "s" when using foreign words, but this should be avoided when speaking actual English (ie Smith in Katakana is SU MI SU).
"blue cheese" - Again, without the words, I mistook it as grilled cheese. He should pronounce the l more clearly so it won't be mistaken for r.
"We also need" - We sounded like they, for some reason. the e sound in we should sound like the e in need, not the a in day.
"Three red bags" - again, see above comments for th sounds
"We will go meet her" - He needs to try not to slur these words together. Of course, most American teenagers slur words together anyway!
2nd speaker
my comments are a little more nitpicky, but that's because I think he's at a comfortable level to fine-tune his pronunciation.
"bring" was a little slurred, and it was hard to catch the b.
her brother bob - the syllables in "her brother bob" were all equal in stress; the first and third syllable should be unstressed, and the second and fourth stressed.
"We also need a small" - the syllables in "also need a" were of the same tone.
three red bags - th sounded a little breathy.
I'd love to try to correct the last two speakers, but I really have to go get my schoolwork done, so I'll get around to them some other time. Sorry if some of what I said were confusing or plain wrong, I typed out parts of it in a hurry...
I'm curious, are these your students? What level are they, as far as years spent learning? Although everyone needs room for improvement, I think they're well on their way!