Duncan, I made a move to Germany about seven months ago from the US. All told, we brought 800 pounds of luggage and bikes with us on the flight.
We first tried to get estimates from everyone, from USPS to DHL to the bulk cargo services. The bulk cargo services were in the thousands, nearing five figures, meanwhile, furniture and other container worthy items were cheaper for the same weight. I didn't get it, so we went ahead with my idea to deal with the hassle of bringing everything on the plane with us. We picked an airline that had high weight regulations as follows:
-two suitcases per passenger, along with a reasonable size limit, 23kg
-overweight per suitcase, up to 32kg: $30/suitcase
-each extra bag, up to 32kg, $125/suitcase
-two bikes in Trico cases, $30/case
-one bike in a suitcase
All told, they charged us only $575 to move all this, plus our tickets. We reserved well in advance, and we bought several 40" duffel bags marketed under the brand name of "Amaro". They are bigger than anything else out there and allow more volume than any suitcase near them.
Your Spot should fit in one of those conventional suitcases that existed before the uprights took hold. Bubble wrap is cheap and don't be cheap on it, either. You will have to completely or partially disassemble the rear tri to fit, compress the fork, air down the tires, but it should work. I couldn't find these suitcases, but had some old ones, luckily, and also was recommended to find them at THRIFT STORES. We packed clothes around this bike, used the wheels to stiffen up the case up and down, and some other things to prevent compression. Came out fine, and in fact, I just took the frame out last night. It took me at least ten minutes to unwrap it and the individual parts.
Other options are the trico case or an S&S case, like Miles E (I think) ran his flux in.
This is provided you're willing to fly back with it. I would.