Before we traveled to Scotland in 2015, we ordered mosquito nets from Streme.co.uk in England. Went very quickly, within a week the order was with us in Holland.
I had bought 2 meters "extra fine" with 20 x 30 gaps per square inch. These holes are small enough to block the little blighters. Color charcoil. This was more than enough to cover the three big tent vents in the attic room, plus the ventilation holes in the top.
Wasn't cheap: at the time it was £ 35.50 plus £ 6 for the post office.
I sewed velcro on the seams of the vents and on the nets, using a bent furniture needle. So the midge nets are removable. Also made one in the sliding window above the kitchen block. This comes at a price: the very small holes obstruct ventilation on warm days. But hey, it's Scotland...
However, the benefit is questionable. You only have to open the sliding door in the evening for a quarter of a second to receive three billion mosquitoes (rounded).
BTW: Here's a travel report on our journey to Scotland, in the wettest summer of the century. Twelve pdf files, in German though...
caliboard.de/applications/core/interface/file/attachment.php?id=31920
Regards from Amsterdam,
Marc.