I crossed the country at York through the Dales on my Dungeness-Durness trip last year. It depends on the route you are taking as to what I would recommend seeing. I don't know if you are going through Reeth- but it's a lovely village. My favourite dales are probably off your route if you are planning on York to KS in a day. If you pass through Coverdale, (unlikely, if you are on your way straight through the Dales) please give my kind regards to landlord of the Thwaite Arms in Horsehouse. (This is a bad joke, by the way, he is not worthy of the job title, drink and eat elsewhere).
I'm guessing you are taking the B7076 up to Moffat, no? That's how I got up into Scotland. My memories of it are not good- but it was completely shrouded in mist and torrential rain on my journey, so my judgement is metaphorically and literally clouded. I was glad to leave it at Lockerbie where my journey took a more westerly direction. I did end up in Ardnamurchan, but via Arran, Kintyre, Islay and Mull, which I would recommend absolutely, but obviously takes tons more time and I appreciate not everyone has that. If you can fit the Kingairloch road (B8043) into your trip, which, if you are indeed using the Corran ferry,
makes the trip from Glencoe about 70 miles instead of 55 or so, it's worth it. A lovely, quiet road alongside Loch Linnhe. Even in summer, on a beautiful day, there's hardly any traffic on this road. About 6 miles south of the ferry, take the B road to the left, instead of carrying on to Strontian on the A road, follow it round back to the A road. Worth the detour.