Here's advice from a tribal arts dealer in the San Francisco area, who's shipped spears (and the small boat I mentioned previously) and he recommends this:
For large things shipped overseas, best to use FedEx but you need to go through a special department "FedEx Great Rates"
Use of this service requires a FedEx business account which anyone can apply for, at no charge.
The Great Rates program also applies to FedEx's "freight" department which is useful for really big, or heavy (like 150 lb or more) items. You need to specify freight if this applies to the size of your packaging, when you use the Great Rates webpage.
My colleague suggests shipping your spears in a plastic (PVC) pipe, they come in large diameters like 6 inches or even more if necessary, in various lengths, available at building supply stores. There are special plastic end caps made to fit each size so this prevents the sharp tips from poking out during transit. The PVC is stronger than cardboard and will guard against the most common hazards encountered in shipping spears -- breakage of shaft or bending of the steel tips.
Since you have to declare the contents for international transport, and considering FedEx's irregular policy on weapons, you will not be shipping spears, but rather things like flagpoles, fishing equipment, or processional emblems. (I would avoid the descriptor "martial arts equipment" which some guys like to use, because some countries restrict things like balisongs, throwing stars, nunchakus, and the like). Couriers like FedEx and UPS tend to interpret things more strictly in order to cover their butts.
I hope this gets your items across the pond without any problems.