Sending insured packages to Canada from the US can only be sent at package rate, not as mail/letter rate. These packages also require more paperwork than letter rate packages.
I will never use the UPS services. They always overcharge me.
Sending books to England from the US, particularly large packages including a hardback book, costs a fair amount of money. Be fully warned.
Zip4 makes post get to its destination SO MUCH QUICKER. Everyone should use it.