I'm not heading the game but if anyone hasn't booked yet I would recommend the Karakoy area to stay in. I've stayed here several times many bars, restaurants round here a local speciality meal is the Fish Kebab! You can walk to the stadium in around 30 mins a long the water there is more here than Taksim square from my experience and Taksim is a bit of a boring place compared to Karakoy. If you have several days in Istanbul I would recommend travelling from the ferry port in Karakoy to the Princes Islands for a day trip or a much easier trip that being across to the Asian side of the city in Kadikoy especially at sunset which is pretty special with the Galata tower and the Mosques in the background. Drinking wise the Asian side is generally cheaper and more authentic experience. Any other questions feel free and enjoy Istanbul if you have a few days it's a city with so much to see.
Just booked in the Karakoy area based on this - thanks 
Brilliant I forgot to recommend where I've stayed twice in Karakoy which is the Ada Karakoy Boutique Hotel has a decent view across the Bosphorus straight.
For anyone staying in Sultanahmet whilst the area has many of the Big tourist sites in Istanbul it also has less bars but many good cafe/restaurants this is due to the fact it has a lot of religious sites in a proximity. If the weather permits I would recommend also walking along the Kennedy Cad road in this area which loops back to Karakoy.
If anyone wants to stay more upmarket or spend time in a more upmarket place I'd recommend Arnavutkoy very fashionable area and also has many boats available to hire in the area.
While the Main Istanbul Airport is closer to Taksim it will still take a while to get there and from experience SAW Airport sometimes can be just as fast. I would recommend using Uber for Taxis in Istanbul as it gives a set rate generally and reduces the risk of getting scanned.
Just a final note the tourist sites are generally very expensive in Istanbul now and if you decide to do them you'll end up spending a lot of Money for example Galata Tower is £30 and Dolmabahçe Palace near the ground is £45.
Any other questions please ask.