Welshpool isn't actually hard to find if you're coming from north or south, so that you can see the length of the runway (22/04). It does tend to be invisible from east or west, but it's only a couple of miles from Welshpool town, so the most you should have to do is circle around a bit in order to find it. Not like some airfields with no obvious features for miles - like Sleap, in the middle of the almost featureless Shropshire plain, or Shobdon, in a similar sort of position in Herefordshire.
And as Daifly said, lovely place to visit, definitely to be recommended.