Here's a breakdown:
* Cockney: This is a London accent known for its distinctive vowel sounds and its use of rhyming slang. While Jessie J's accent doesn't have all the classic Cockney features, it does retain some of the characteristics like the "glottal stop" (replacing the 't' sound with a glottal stop, e.g. "bo'tle" instead of "bottle").
* Essex: This accent is often perceived as a more "street" or working-class accent, sometimes perceived as "rough" or "uneducated." While Jessie J's accent has some Essex elements, it's not as pronounced as a purely Essex accent.
Ultimately, Jessie J's accent is unique to her and a blend of influences from her upbringing and experiences in London.