I'm in a very similar position trying to build up a window list from my terrace house in old trafford. There are very few trees or greenery of any kind. We have a tiny backyard with a few feeders, but generally no birds on them, other than occasional blue tits and goldfinches. I have had grey wagtail on the roof opposite several times and a sparrowhawk patrols the area regulalry, but most of the time its very slim pickings...
I am currently forced to spend my time at home in my terraced house and Paul has suggested a 'window list'. So far that would go BH Gull, Magpie, Starling, Feral Pigeon and sometimes House Sparrow. There is not a lot to be seen in such a cramped urban setting. Or so it seems. I think maybe I could get a bird table and some feeders but when I have tried before with feeders getting into a position where you can see the birds from a downstairs window means they can see you too and promptly disappear but here upstairs in front of my computer I have a partial view down into the yard (standing up only) and over the rooftops and into yards the other side of the alley. Mistle Thrushes stand sentry from the front door on the roofs opposite and Goldfinches sometimes use the new trees on the street. Back last year I nearly had the Parakeets on the 'garden' list as they came over the street when I was about 20yds down it on the way to work. So there is hope.
There we go 3 more BH Gulls over and 3 Feral Pigeons!