You might be able to get away without crating the bikes. Just put them on a suitable pallet and ask the airline to provide a container (ULD) to hold them. If the airline is hungry enough for the business, they'll do this at no charge.
Typically, for motorcycles, you cube out before you weigh out. But, if the airline has empty space in the belly, they might just cut you a deal and charge you only for the weight and forgive the cube. The tradeoff for this is you have to let them pick the date that they ship, which can be as quick as same day or as long as 7 to 10 days after you drop it off.
Go looking for an airline that runs widebodies (I know SAA does, certainly in and out of ZRH, probably to the UK as well) or combi's. That's the size of plane you need.
You can see a picture of a container at this thread: Flying bike from Europe to Nairobi
[This message has been edited by PanEuropean (edited 24 March 2002).]