Wow Grey Mares Tail is well worth a visit just off the motorway a few miles from a pretty village called Moffat Southern Scotland . We ventured here from our base in Ullswater surprisingly only 1 and a half hours away. The walk up the side of the falls is well worth it. The views of the lock at the top are stunning. We we're fortunate to see 2 ospreys flying around the loch. We later found out that the local park ranger had been camped up their until our stay to picture the birds and missed them. Anyhow here's a couple of pics.
The road from Moffat to Peebles is superb, better still on a motorbike or something quick but very scenic whatever, better route to Edinburgh than the motorway.
That's just down the road from us. Glad you liked it. If you keep heading towards Peebles from there you'll get to St Mary's Loch, which is also very pretty and has a campsite attached to a pub right on the shore. Well worth a visit, and like you say, it's really not that far from Englandshire.