6 is a good number, allowing for group activities ( 2 groups of 3, or 3 groups of 2)

Students need to be of a similar ability, so that they don't become discouraged or bored.

If you miss a one-to-one class, you can reschedule the lesson at an agreed time within 4 weeks. If you miss a group class and the rest of the students still take the class, unfortunately you forfeit the class - although I can supply a summary of the topics covered. If the class itself is cancelled, it can be rescheduled at an agreed time within 4 weeks.

Except in an emergency, please let me know by 21:00 (00:00 GMT) the previous day

Sorry, students should be 16 or over.

How long is a piece of string? It's impossible to say accurately how long it will take to become fluent. Everybody is different. However, additional self-study will help accelerate your learning. Together with regular classes.

Payment can be made by cash, bank transfer, and through Paypal. It's standard practice among private teachers for lessons to be paid for in advance.