Hi Damo,
Personally, I think it really needs cropping, as currently the focal point of the image isn't really apparent. The bridge is an interesting lead into the photo, in the sense that it comes in from above, where normally you'd expect a lead in to be at the bottom.
The black and white conversion is also very flat. You've also got some over exposure in the sky, which you might be able to address if you shot this in raw format, as it will allow you to recover quite a few EV depending on the model of camera.
I had a quick play with your image in photoshop. Cropped it down, placing the dome of St Paul's (think I'm right in labeling it as such lol) on the left had third line of the photo and the bridge leading you across to it. I then dodged and burnt the image to improve the contrast and bring out more detail, before apply an unsharp mask and finally a high pass filter.