I've been recommending this resource to many learners and potential learners of ESOL and even English Functional Skills.
It allows learners to submit some typed in text for a particular task (for free) and then get feedback. They may need some help understanding the feedback, if they're not sure about grammatical terms, but many of my learners have found this very useful.
I have started to give it out at the beginning of term for students to get extra writing practice outside of the classtime.
I hope you and others find it useful.