Cranes are not a native species which makes it an unlikely visitor.
Working exclusively from your picture which shows black areas in front of the folded wings and such a tall pale coloured bird, it's hard to imagine this not being a grey heron.
Small numbers cranes are known to migrate across the south east of the country during spring and autumn, and there a couple of projects to establish native bereeding birds so its not impossible. At approx 4 feet tall cranes considerably taller than a heron (about 9 inches taller) but standing on a rooftop with only ridge tiles to compare against for scale, either would look enormous. Also note that a crane would have a distictive black neck.
How tall would you say it was? What colour were its beak and legs? Where abouts did you see this? There may be details you can give that you saw but don't show so well on your picture.