I think that fairies would be really good at things like keeping greenfly down an pulling off wilting petals but nothing too strenuous. Leprechauns can do heavier work but they like a Guiness or two at the end of the day.
i think fairies too, i wouldn't bother with a house elf, they are not as helpful as they are on harry potter, plus they have a habit of wearing my clothes.
Now Leprechauns would be a nuisance, can you imagine all your pound coins disappearing.