I was in Kielder this January, when it was bitterly cold, so no midge problem at that time. However, on the bus-ride to Bellingham, the driver spoke at some length about how bad the midges could be in the summer.
Mind you, I'd be more worried about getting involved in a game of football in that area.
According to local lore, the first 'international' game of football was held in the area, following the cancellation of a grouse shoot, between the retainers from the estates of the Duke of Northumberland (England) and Duke of Buccleuch (Scotland), around 1790. The final score was England 2 - Scotland 0. There were eight players killed during the game and several more died afterwards as a result of their injuries.