Oranger a bit late but I suggest you find your local Avon agent and buy soap, dry body oil and shower gel in their SSS range. It must be the Woodland Fresh one (green containers). I speak as a local and these really work. We have tried a number of different products over the years including some recommended for travels in the jungle but these Woodland Fresh are the only ones we have found effective. Enjoy your holiday.
How long is a piece of string?. El Midgie is temperature dependant. One moment they're there then they're not. Anything over 15 degrees and you're fair game to them! Enjoy your stay in the highlands, there are worse critters in the world to deal with on holiday.