We had and amazing stay at Madalena Guesthouse. The room was very spacious and clean; there were lots of amenities such as shampoo/bodywash/towels etc. The location is very central and there are lots of nice stores and restaurants within walkable distance.
Something to note is that the walls are very thin and so sound travels very easily from the other rooms, so I would recommend bringing earbuds with you.
But I would definitely recommend this place if you are looking for a wonderful stay in the centre of Lisbon!