I used Interparcel to ship a 20" alloy wheel with tyre. It was through UPS's service, and cost around £25 I think, (with insurance).
Great service with no problems
My BMW Miniature Collection: www.bmw-miniatures.co.uk
Past: BMW E90 M3 LCI | BMW E60 525i M Sport LCI | BMW E92 330i SE | BMW E60 525d M Sport LCI | BMW E39 530d Sport | BMW E65 730d Sport | BMW E90 330i M Sport | BMW E39 525d Sport | BMW E46 320d Sport | BMW E46 325i Sport | BMW E46 320d SE