I cant really comment on the squatting v cocking debate - I think that it does come naturally eventually, but those who have boy dogs will know better than me and my girls
Although I dont think Bramble's bits will freeze to the ground, Sue
re the original question and your two dogs of 15 months still soiling at night... well, I think this is one of the difficulties of trying to train two pups of the same age, at the same time. It's a lot harder, partly because they can bond very closely with each other, and partly because there's a bit of a circle going on - one pup wees, the other thinks its okay and wees too, then the other pup thinks its okay and so on.
I'm sure you do all the following anyway, but I'd just tighten their routine up a little more, if possible, by: limiting the amount of water they have at night (though stil leaving some); by going to bed a bit later and getting up a bit earlier, if possible; making sure they both go out and do their busines before you put them to bed - you might want to do this one at a time as it could be easier; possibly using a different cleaning solution to mask any odours left by their existing soiling - you'd be amazed how powerful their noses are.
Hope you find this useful