Using the post code and Satnav can be very unhelpful as it can indicate that you have reached your destination when there is still the best part of two miles to go. Coming from Presteigne it is more helpful, but the easiest way is from Knighton. If you head out of Knighton on the A4113 Ludlow road, before you leave the 30 mph limit you turn right up the Llanshay Lane and go up the hill past the Observatory. Bear left at the first fork, right at the second and that will take you down to the car park (over the cattlegrid) and house on the right.
Coming from the east on the A4113, five miles before Knighton you pass the turn to Bucknell. A quarter of a mile further on, take the first left into an unsigned lane (Reeves Lane) between two cottages. Go two miles up the lane until you come to a sharp left turn which takes you down to Hill House Farm.