An addition the original Marylebone mini-chain, Vinoteca King's Cross doesn't suffer from a reduction in quality or ambience. I imagine it would be extremely easy in this location to be rather lazy, assuming that most diners passing through will be never-seen-again tourists. But the welcome was warm, the service was attentive without being intrusive and they were very happy not to turn our table enabling us to while away the afternoon and of course spend money on wine!
We had the great value set menu for lunch and the food was truly yummy, with fresh fish not overwhelmed with butter and a fresh, crisp salad starter. They are really happy to accomodate allergies and are fairly vigilant about it, which is great.
The best thing is that you don't feel like this is a "waiting room" for people catching trains. It has a warm atmosphere and you do forget the location. As with all Vinotecas, the hard wooden seats are still penitential!