@ Beccarose: When we moved to the US in 2000, we arranged our own container with ACL, and used the container line's clearing agent in the US. From the US to the UK last year, it was M&S Shipping in Norfolk VA, and the agent on this side was their regular guy in Liverpool, but I can't remember his name. We had direct quotes from the same container line, but M&S gave us a CHEAPER quote for the same service. And, they were fantastic folks, and knew their stuff.
As for packing early, you might be amazed how long packing takes. And how many more boxes you need. You will also be surprised what you can do without. We stated packing about 5 months ahead of the move, beginning with knickknacks, books, out-of season clothes, shoes, etc. We pared it down as much as possible to basic kitchen stuff, but planned the packing for that, clothes and linens. I was working, so computers were active until the last minute because I had a home office.
We numbered boxes as K-1 to K-xx for kitchen, B-1 to B-xx for books, and so forth. A lot were 'miscellaneous' because they had bits of this and that. Numbering and having a detailed list minimizes your chance of a random custom check. The shipment needs to be in the name of the person who is a citizen; this minimizes exposure to duty.
We had a 40' container, so we took almost everything, but gave away and sold furniture, some electrical items etc that we knew we no longer wanted, wouldn't use etc. Then, after we got here, the British Heart Association got a VAN LOAD of stuff that we should have dumped in the US. But - a container is a container, and it didn't cost more to ship the stuff we dumped on this side.
Hope that helps.