Thank you, where am I likely to see them perched, trees , ledges , rooves?

They were Ring-necked Parakeets Mike. There is a sizable population in south Manchester.

On Monday 14th September whilst driving on Greenheys lane ( near the brewery) off Princess road, 7.15am, a flock of swallow type birds (about 30) crossed in front of me at windscreen height, they were twisting and turning like swallows but there was a definite bright green colour on them. What would they have been please?