We have two harps, a nineteen string and a twenty nine string, both made in the USA by Stoney End. I think Hobgoblin still stock them in the UK. The smaller harp is a little limited, they are both lever harps, so accidentals are possible mid tune. The large harp is still smaller than a double bass and the other is not much larger than a dreadnought guitar. Playing slide harp is brilliant, check out Joanna Newsome.
O' Carolan's music was introduced to me by a musician friend many years ago, Joe plays classical guitar and his version of Planxty Irwin is well known around here. I manage a reasonable bluff at it on cittern . . .