However, I did explore the Taksim area, I did go to the Grand Mosque and Hagia Sophia and I did spent some time in the Galata area. When I worked out the public transport system, it worked well for me - cheap but a bit crowded and I did enjoy a couple of fine lunches, one of fish and salad and another of adana kebab and salad.
I will have to return in better weather, early May has been recommended to me and may well be do-able next year.
The hotel is quite recommendable, on arrival I was upgraded to an Exec Floor Bosphorus view, which was great and I spent quite a bit of time on the balcony, which meant that the room didn't get too smoky. There was fruit and water for free on arrival and the fruit was replenished most days. Nice toiletries as well. The slight down side was that there was a nightspot below my balcony and that was a bit noisy on the Friday and Saturday nights.
The Exec Lounge was a delight, with attentive staff, a wide selection of beverages, a lovely selection at breakfast (I liked the spicy veal sausage) and nice hot appetisers. I'd certainly be happy to return there.