Tulip guesthouse offers a good location in Sultanahmet area (old Istanbul) with clean beds and Free Internet connection. It is of 5 mins walk from the main attractions in Istanbul as well as the Sultanahmet Tram station which can take you wherever you want. You are also offered a drive to the airport for 5 euros/person which was quite cheap and punctual might i add (but this service is pretty much offered by all the "hotels" in this area). Helpful staff although the reception is not 24/7 sometime not at all.
But i would have to point out that even though June is considered to be the high season in Istanbul, paying 240 euros for 4 nights for a double room (which could be easily described as a single room due to its small size) is a bit pricey for the guesthouse.
Overall, if you are looking for a well located, clean B&B, Tulip Guesthouse is recommended.More