I'm a full instructor, have been for 15 years and instruct for 2 days a week, I only get £17/hr and no retainer or travelling expenses! I think the only way ahead is to teach commercial or do private tuition for PPL's on their own plane i.e tailwheel, aerobatics etc then you can charge £35/hour or more. Trouble is building the contacts to get regular work. Does make one wonder if it's worth the expense of renewing the instructor ticket