Lost blue parakeet named Sky with a yellow beak in Essex park, United Kingdom.

I lost my blue parakeet named Sky while we were out in the Essex park last afternoon. He flew out of his cage while I was setting it up for some fresh air, and I couldn't catch him in time. Sky is friendly but may be a bit scared. He has a yellow beak and cheerful little chirps, and he really loves sunflower seeds. If anyone finds him, please let me know!