Once you visit Koya-san it becomes clear that there is fairly standardised way of staying. Get a 2 day park pass, train to Gokurakubashi, cable car and bus to a temple - most of which are closely colocated along the main road in koya.
Henjokoin was easy to find from the bus stop and the monks were welcoming and explained where everything was. Traditional room atmospheric and minimal with paper sliding doors (we did not see the need for TV .
Dinner was served privately - and it was a beautiful selection of vegan dishes and an early night.
Prayer was short and ended with a short talk about the temple.
Would recommend it for a one night respite during a busy trip.