I thought maybe this would be interesting.
Spoken to Close Aviation now and basically they finance against the aircraft, but quite conservatively. They look for re-salability. High time engines, high timed aircraft are obviously less attractive.
They said that for a very common type of aircraft, like a Cessna, Piper or Cirrus, 20-25% down is the norm. For more exotic types that there isn't a huge base of in Europe (like the Lake), it'd be around 30-35%. The loan runs over 5 years and can either have a ballon payment at the end, or be mortgaged down. It is possible to remortgage for engine service and upgrades. They didn't want to give me a rate (as it's variable), but they said it'd be in the range of a "car finance APR".