Our best idea so far is a land anchor and ratchet strap and let it down onto the ground below the wall, which is pretty solid, then dismantle and lift over the fence by hand. If anyone has any better ideas, please shout!
I can't get any machinery down to it on my side because of the angle of hill and deep mud - it simply won't get back up again. I can't get any machinery down on the neighbour's side because she doesn't want me to make a mess of her field (the house is up for sale, they don't live there any more). It's gone over two fences about 2.5ft apart with a dry stone wall in the middle, so dismantling it isn't really an option either (and I don't think I'd get permission to take their fence down, though I'll have to re-do the one it landed on).
From our side:

From neighbour's middle field:

From neighbour's bottom field:

Closer up. There's about 6/7ft between the point of the shed roof and the ground:

Plus it's nicely wedged on the wall and some broken trees and a sheep netting fence:
