I have a part time job I do Monday to Friday in the mornings up until lunchtime. Saturday and Sundays are Instructing days, and I also fly in the afternoons when needed. That is the only way to keep the head above water financially as instructing pays so little and the is no guarantee of work. Best month I have ever had Instructing I earnt £650.
The down side is days off, where you have a complete day of no work, are few and far between, and that makes you tired after a while
I think £20/hr for teaching PPL is not unreasonable in the present market. £25 for Night/IMC/Aero. £40-£50 per hour for CPL/IR. Retainers should be sufficient to cover travelling expenses and food. £15 a day not unreasonable.