"on the 5th of November" is practically just removing the word day from the reference. As in "on the 5th (day) of November." It is used everywhere and even though it could be understood a few different ways it is the most correct. "on the 5th November" seems to me to more be dependent on the month and if not year. As in "it's my baby's 5th November" as in, the child is experiencing November ...
