Islington Swifts Group are helping me install a nestbox for swifts, as these birds are becoming endangered as they lose nest sites in older buildings. The group might be able to help install boxes on your home too, if the building is suitable, and they can also give advice about doing building work which protects swifts. They're also interested if you know of current nesting sites as there is very little information available at the moment. You can contact them on firstname.lastname@example.org. They also have a website and Twitter account: https://islingtonswifts.wordpress.com & @islingt_swifts. There is a Haringey Swifts Group on Facebook where you can also share sightings.