Anybody know how to send parcels to the US cheaply?

[Avago]

I'm sending stock to amazon in the US and don't mind if it takes a month to there but all options I can find on Parcel Monkey /Parcel 2 go etc are a few day courier service. It's just cards & gift wrap, so not big and not freight quantities. Any ideas? Thank you !

How big is the item? You can use Royal Mail's surface mail for packets up to a certain size, and that is estimated to take six weeks to deliver.

Thank you.

I'll be sending multiple boxes of about 33 x 33 x 45 but I can increase or decrease to whatever is most economical. I thought I would be sending 1 big box however with Amazon if you have 2 items the same to sell they want you to send one to one side of the country and one to the other. It makes sense for them but couriering 3 bundles of cards to different addresses almost made it not worth doing last time. I need to work smarter this time as I'm sending a lot more and what to make money! I think of Royal Mail and Parcel Force as the same - am I wrong ? Parcel Force Air mail are on the comparison sites but massively uncompetitive. I'll go and look at Royal mail site.

Thank you for your help!