You won't get many replies as we can't talk about nic since the tpd law changed. A trade account is now required to buy 7.2mg but ive no idea on pre mixed.
100mg would require a poisons license in the UK and if you try to import it without one, you'll find yourself in some hot water. 72mg is the common strength cause of that.
72mg is an odd number now that I think about it. Why not 90 or 95?