Nope no charge -
you pick them up at the pool reception. You have a choice of walking to the pool in your complimentary DLH robes, or changing when you get there. If you prefer the former you might want to ask for a room in the same wing as the pool (the east wing as far as I remember) or you'll have to walk past all the restaurants in your robe to get to the pool - plenty of people do it though