Enough has been said of how brilliant the flat itself is, so I won't gush on but will echo that every positive thing said is true.... and then some.
I'll add that I was fortunate to spend a month at The Saddlery, without a vehicle, and you will not find a more central spot for exploring not only Co. Sligo, but all the neighboring counties in the area via bus or train. Even Dublin was a convenient and easy day-trip!
Collooney itself is the most ideal location, with every convenience you could want, and the bonus of having the nicest and most genuine folk you will find anywhere.
The only hard thing for your entire stay will be leaving. Wendy and her vast knowledge of the area makes everything else as easy as the countryside is beautiful.