I would say it depends upon where you're going. I've arranged sea freight for expeditions to New Zealand and Papua New Guinea and both times used the same shipping company. I won't give you their details because they were shite! But essentially it's not hard to find a firm that will send your stuff abroad. Dozens of them around Heathrow. Lots of things to take into consideration for shipping/air freight, though, including type of containers (some countries don't accept crates made from certain products, I think), bill of lading, insurance, etc... You need to allow considerably more time for shipping than the agent tells you, though, but this can obviously lead to storage issues if it arrives too far ahead of schedule. Probably not such a concern with air freight.
In NZ we got a friend to nip down to the port and do the customs paperwork. Just had to produce the bill of lading, I think. In PNG we had to use a local company to deal with the customs clearance and it was a long and tedious affair. I imagine that it's not going to be too dissimilar for air freight. So again, depends where you're going, I'd say.
Both times it was sea-freight rather than air freight. I might be able to advise more depending upon destination as have plenty of contacts in various places. Oh, and I know a CDG member who is a commercial pilot so he may be useful.