I don't suppose there is much we can do: his land is classified as
agricultural land, so sawing wood is part of the brief, and in any case we
would not like to fall out with them - but short of planting a forest
instead of our garden, is there anything we can do to hide the eyesore and
minimise the noise?

--
Klara, Gatwick basin

Depending on the amount of garden space you have, your proximity to the
boundary and what direction is South, I'd be tempted to go for a row of the
dreaded leylandii. It does have it's place depending on the circumstances. I
don't know how much noise they would block out but would be better to look
at than an asbestos shack. There are probably climbers that you could run
through the trees to make them more attractive and help block more noise
too.
The denser and taller the foliage the less the noise.

David.