The easiest way to get over to Tanygrisiau is predominantly along the A5 via Llangollen. However for a fabulous scenic route with two mountain passes take the most 'direct' route, turn off the A5 before Oswestry signed to Knockin. Then take the route of the B4391 to Bala and then part of the A4212 before turning off again towards Blaenau Ffestiniog. The GPS kicks in with this route if you turn off the A5 between Shrewsbury and Oswestry