You would be welcome to some but i thought fry were sensitive to different water temps. A couple of days in the post in this weather would surely kill them off?
with a heat pack and a bag of warm water and the polybox i think the temp stays quite static, and fry produce so little ammonia that they travel much better than adults, you could wait a bit longer until night time temps pick up a little, id really love some. di wouldnt want them to die though