If you report stuff to the Council they do tend to sort it out. So i have reported about a dozen grafitti tags, illegal posters and some fly tipping in the North Kings Cross area over the last 24 hours (Gifford Street and Carnoustie mainly). Usually a simple emil to contact islington (contact@islington.gov.uk) with a precise location and a photo does the trick. Or you can use the excellent Fix My Street service. If it doesn't get sorted in a few days then just keep hassling gently until the work is done. Basic stuff seems to get done rapidly these days.
Some problems though are intractable and you have to nag away for months, even years. The website can help here – by keeping an incontrovertible public record of when things were first raised. This episode with a street light for instance.
I have just noticed that two broken downpipes under the Ferodo bridge has been fixed in the last few months – they used to flood the bus stop area in the rain. I raised this over two years ago but it took Network Rail ages to sort it out. Persistent polite nagging and involving the Council were vital. Kings Cross has lots of big problems, but you have to tackle the small things – together they add up to a bigger picture.
Kings Cross Environment 
The tag (in Will’s photograph) that has been appearing everywhere around the Bemerton estate and adjoining streets is a new one. There have been dozens of these found of walls, doors and, yesterday, I saw two vans that were defaced. There are several theories about who is responsible … either some new kids living locally or some others who have decided to choose this neighbourhood as their graffiti zone. The Bemerton caretakers have been cleaning off dozens of these tags but also gathering reports from residents on the estate about sightings of the villains responsible. All leads will be gratefully received.