Surely you can argue for a shed on environmental grounds:
- it will reduce car journeys, because you wouldn't need to drive your tools up every time; so you could cycle instead
- you would use less water, because you could have guttering off your roof, and collect rainwater in butts
- you would also get more work done, because you could shelter from showers, instead of going home when it rains (& driving back again when it stops)
If the council is worried about unsightliness, they could specify sheds have to be of a specific size and type, and possibly colour (blue?
)