My partner and I had the most wonderful stay in Syros at Manos' place. The house is just like you imagine a cycladic house to be and very spacious. It's super nice and cool in the bedrooms downstairs but still light. It has all the amenities that you need, including a washing machine and a drying rack so you can regularly wash your swim stuff.
The place is located at the top of a hill which means you get the most amazing view, day and night, from the terrace. It's very private and you are never disturbed. It's about 10-15 minutes walking to the sea and the center, down a lot of stairs. To get back up, you can also take the stairs (but very hard on a hot day) or get a cheap taxi for about 4€.
We stayed for 2 weeks and it was wonderful. I wish we could have stayed longer and I definitely want to come back. Syros is gorgeous and all the people there are super nice. Manos is a perfect host, quick to respond and helpful with many tips.