Hard to find accommodation for larger groups in Lisbon (we were 7, there for a bachelor party, apologies to the host if we were a bit loud) but the Garden Guesthouse did the trick and beat expectations. Place was very well-kept, well put together, and staff was friendly.
Breakfast could be improved but it was edible.
Note, the location is a bit out of the way. ~15 minutes to Barrio Alto by car. I was aware of this when I booked.