FWIW, some routes I used last week for a S>N>S trip in Wales. All on road, used some of the Lost Lanes Wales route book for ideas, some of the LL sections are in green but I didn't get round to colour-coding the later routes when I realised they didn't show up on my Garmin in that way.
- Severn to Tregaron inc Abergavenny LL routes
- Tregaron to Bala
- Bala to Long Mynd via Llanberis pass
- Long Mynd to Stroud
The rides between Stroud or the Severn and home in the Chilterns not included, probably not of interest here.
I took a few diversions, one was to miss the climb then long descent to Machynlleth in the Tregaron-Bala section (that's part of Lon Las Cymru). It was raining and I went through Pennant instead and carried on to the Bwlch. Then the weather cleared so I had time to descend E from the top of the Bwlch, down to Vyrnwy then back up and down to N end of Bala. That was a good alternative section and worth riding the other way on the return leg of Bala-Long Mynd.
Also on that file I went to Devil's Bridge which was a few miles off-route and took me into the Ystwyth valley perfectly.
The other diversion was after Long Mynd where I straightened the route in places to gain some time on a slow headwind kind of day.
All in all a really enjoyable ride. There weren't any bad roads, even a few A-roads that were really quiet considering in the SE I won't go near A-roads at all.