We have the same problem and it is driving me crazy. We also tried the next size up and he was wet within 4 hours. Funny thing is, it doesn't happen every night and I have no idea why. I was going to try cloth nappies too if it kept happening. Good luck and would love to know the answer. I was even considering putting in a panty liner or pad into the nappy where he leaks to absorb the extra wee...... So hard changing everything in the middle of the night. Aldi nappies don't work with my DS, he wees through them during the day.