Many thanks for adding the 'uksm' tag, your recording's now on the UK SoundMap. Jet aeroplane noise really is an almost constant feature in south-west London during the day. Like you say, it somehow seems to spring out more when you listen to the recording than in real life.
A lovely sunny afternoon with just the rustling of wind in the leaves when my meditative cup of tea was interrupted by the ubiquitous aircraft passing overhead. I might not even have noticed but for having decided to record the ambient sound.