Just to balance the Wales/Scotland experiences. Been to Scotland 3 times camping, (in a frame tent not glamping or staying in chalets/static caravans etc).
We stayed in the Fort William/Oban areas, each time in early to mid September, and each time had glorious weather for the 7 days each time we were there.
Wales was pretty much the same. Lost count of the number of times we have been to Wales including North Wales, (Llandudno, Ruthin, Conwy, and Amlwch on Anglesey), and central Wales around Trawsfynydd, Betws-y-Coed, Llangollen etc Not saying wall to wall sunshine but certainly no horrendous weather except for one trip to Llanberis during an early spring. We were camped on a steep slope right in the middle of the pass and it was quite windy on the evening of arrival and a b*tch of a job to erect the tent but we managed it. Went to bed in our sleeping bags and woke up to a bright sunny morning, so bright it was even penetrating through the outer tent and making the sleeping quarters very bright. Then a cow started nuzzling near the zip so my cousin opened the zip and came face to face with this massive cow! (We were only about 14 at the time). Thats when we realised the outer tent and frame had been blown away during the night. It was laying in a crumpled heap against a stone wall at the bottom of the field. That put an end to that trip and we had to return home the same day.