I've been looking everywhere but cannot find it/ settings/ mod.

I want to set up per item, per zone postage that decreases the more you buy and has multi zones.

Example:
Buy 1 to post to UK - Postage = £3
Any item after that is £2 postage

Buy 1 to post to US - Postage = £4
Any item after that is £3 postage

etc.

Any ideas?