we did this 6 months ago, but not from the UK.
Rotterdam - Toronto (via Montreal)
Have to admit: we didn't have to search for a company to do it, as my employer agreed to put our bikes in one of their containers!
But still, I had to 'make sure the shipment didn't delay because of our bikes' so I did some homework.
I couldn't get a good answer from Canada what I had to arrange for a smooth import. 'That depends on the customs officer on duty' was the official answer I got from Canadian Customs! :-S
- For container shipments: battery disconnected, and we took all fuel out.
- MAKE PICTURES OF EVERYTHING; by showing our 'look-how-clean-the-bikes-are-during-loading-them-into-the-container' pictures to Canadian Customs we could arrange to skip the 'inspection for mud and dirt' as our bikes had been used in Europe. This would have cost us an absolute fortune (as this would have delayed the container for half a week).
- As this was a shipment combined with commercial goods, only us in person could clear the bikes at customs. Luckily the container was delayed, and we got a 'get your ass to Canada call' one day before our actual flight. Don't know how this is when you crate them. In the end, they never asked for ID so I do not know whether we really had to be there.
I couldn't find out when I had to have 3rd party liability insurance; on arrival in port or on the first day of driving on the road.
We had it started a few days before arrival to avoid issues, but this wasn't needed. Think customs doesn't even care...