I've done the changes for World Zone 10 (USA) if anyone's interested but only for datapost.

In admin>modules>shipping>international datapost>edit then go to the box for World zone 10 and replace the prices/weights with:

0.50:43.99, 1.00:47.79, 1.50:51.59, 2.00:55.39, 2.50:59.19, 3.00:61.79, 3.50:64.39, 4.00:66.99, 4.50:69.59, 5.00:72.19, 5.50:75.09, 6.00:77.99, 6.50:80.89, 7.00:83.79, 7.50:86.69, 8.00:89.59, 8.50:92.49, 9.00:95.39, 9.50:98.29, 10.00:101.19, 10.50:103.79, 11.00:106.39, 11.50:108.99, 12.00:111.59, 12.50:114.19, 13.00:116.79, 13.50:119.39, 14.00:121.99, 14.50:124.59, 15.00:127.19, 15.50:129.49, 16.00:131.79, 16.50:134.09, 17.00:136.39, 17.50:138.69, 18.00:140.99, 18.50:143.29, 19.00:145.59, 19.50:147.89, 20.00:150.19, 20.50:152.49, 21.00:154.79, 21.50:157.09, 22.00:159.39, 22.50:161.69, 23.00:163.99, 23.50:166.29, 24.00:168.59, 24.50:170.89, 25.00:173.19, 25.50:175.49, 26.00:177.79, 26.50:180.09, 27.00:182.39, 27.50:184.69, 28.00:186.99, 28.50:189.29, 29.00:191.59, 29.50:193.89, 30.00:196.19

then update and it's sorted.

If anyone's bothered doing the rest of them and feels like sharing it'd be appreciated :)