I currently rent 2 single garages in Haddington from East Lothian housing association which I'm handing back to them.
Roughly £42 per month. Nice and dry and plenty of housing around so pretty safe. No power or water though.
don't know if that's any good to you ?
Or if you need a larger space, give RP Slight a call in Wallyford Industrial estate. I've just done their electrical testing for them and a few of the units are empty and up for rent. Not sure on prices but they all have lighting and power and the industrial estate has cctv.