Anyone else have trouble with damp sheds or workshops?
Been having condensation issues with my Keter shed that I use to store a couple of my bikes in.
I've been happy with the shed, but I get condensation dripping from the plastic roof, probably a combination of plastic and it being black.
When the sun eventually comes out the roof heats up causing condensation to form and drip on the bikes at times.
Last year I fitted two vents, one low level and one high to create air flow, but it didn't really help.
I did a bit of research and this is what I came up with or copied from others.
I've just installed a large car radiator fan rigged up to a couple of solar panels and a controller, timer and speed controller.
It's a bit over the top, but hopefully it'll keep the damp out of the shed.
Total cost was about £100, I upgraded to two panels as I want it to work all year round including overcast days.
I hadn't planned it but a side effect is I can now maintain bike batteries over the winter. 
Shed solar powered ventilation

Nope.  I have a couple of  keter sheds.  One housing a couple of pushbikes, the other housing the missuses gardening stuff.  Cannot ever say I noticed any damp problems.

I put a dehumidifier in a similar situation, garage with steel ceiling, but I have line power. I only really use it in the summer when the humidity really gets bad, southern USA. Totally solved the issue. Maybe a heavy extension cord might do ya? Three or four bags of DampRid can help too.

Hi,
As per the others I have used a dehumidifier in the past and also the standalone dehumidifier bags. You just hang them up. Not sure how effective they were.

Also used small tube greenhouse type heaters to prevent damp in a wooden shed before, but you need power of course.

Main shed I lined with membrane and insulated, not sure that is practical for you.

Good luck.