I've checked with the post office and you CAN use the small packets services. Apparently a small packet is anything up to 1.5 meters length and 3m circumferance, which sounds likely a bluddy crate to me!
So the prices using "small packets" services are as follows:
Shipped inside original box wrapped in brown paper (1.5Kg):
USA
£19.77 Airmail small packets (from 5 days)
£24.97 Airmail small packets signed for (from 5 days)
£11.82 Surface mail (from 56 days)
£17.02 Surface mail signed for (from 56 days)
Germany
£10.56 Airmail small packets (from 3 days)
£15.75 Airmail small packets signed for (from 3 days)
£11.83 Surface mail (from 14 days)
£15.26 Surface mail signed for (from 14 days)
£17.37 DHL Road Freight (from 2 days)
Shipped inside another box to protect original packaging (2Kg):
USA
£25.54 Airmail small packets (from 5 days)
£30.74 Airmail small packets signed for (from 5 days)
£14.89 Surface mail (from 56 days)
£20.08 Surface mail signed for (from 56 days)
Germany
£13.18 Airmail small packets (from 3 days)
£18.38 Airmail small packets signed for (from 3 days)
£14.89 Surface mail (from 14 days)
£20.08 Surface mail signed for (from 14 days)
These services all include £41 insurance - it costs extra for additional compensation.
eBay demands that sellers use a signed for and trackable service, which some of the options above are not. As postage is prohibitively expensive otherwise, I will use some of these cheaper options (with or without additional insurance), depending on which the buyer prefers. But if the buyer chooses an option without full insurance or without "signed for", they must understand they do so at their own risk.