We had a terrible experience with an apparently OK cocktail bar in C/ Barquillo 40, between Barrio de Justicia and Chueca.
The patrons are a mix of old people who can afford a to take their trophy wife for dinner on weekdays and groups of office workers who stop by for drinks. The bar can sit 20 people distributed in 6 tables. They have an area with couches that can hold 12 people.
We booked dinner for twelve people with 15 days in advance. The day before we had a phone call at 22:00 letting us know that they had accepted the booking a group of thirty people at the same time so that they would have to close the venue to host them and try too fit 2 large groups!
You can find on all the yellow-pages directories: 11870, eltenedor, yelp and tripadvisor.