Back in July 2004 we did a 1500 mile tour of Scotland going via Fort William to Ardmir Point just north of Ullapool and across to Pitlockrey and down to Edinburgh. We had a stop over at Glasgow (steeps) which I couldn't recomend but otherwise had a fantastic time except for the midges!!
By the time we had got to Fort William, I had been bitten over a hundred times, which caused me to seek advice of the local doctor. I was borderline hospital admitable but declined that as I was leader of our family troop of 4 caravans and the other's couldn't navigate a supermarket carpark let alone the Scottish roads as even the A road to Ullapool can be challenging for cars with caravans as it get's tight in places.
The Doc gave me an injection and advised to got to the chemist next door and buy some DEET Oil. This works brilliant but is a perfume to be "aquired"??? Avon skin so soft woodland fresh is a good repellant and you don't smell like a woofter either.
Some of the locals swear by marmite smeared om the lower legs but I don't know if it works or is just a rouse to ID the sassie english
My sister lives at Ayr and she say's the midges are virtually gone there.
Good luck with your trip.