What's an "ESOL", please? .... It's not a qualification I recognise.
As has been noted, "ESOL" is just an acronym used in the English-teaching world. Others are "EFL" (English as a foreign language) and "ESL" (English as a second language).
The most recognised teaching qualification which uses "ESOL" is CertTESOL - Certificate in Teaching English to Speakers of Other Languages. It's issued by Trinity College London upon successful completion of a 4-week in-class course conducted by an accredited school. It's considered by most English language schools as being on a par with the Cambridge University CELTA (Certificate in English Language Teaching to Adults).