Well cesspit, situation depends on whether or not this company will pay you a decent salary. For example, I was working at a school in Scotland part-time and earning £35 per day retainer, £15 per hour, £10 groundschool. As the winter and bad weather approached (shorter days), I took a job full time with the same company, who offered around £1400 per month plus IMC and night flying bonus. The trouble in the Instructing world at the moment (certainly in Scotland) has a lack of instructors with in excess of 700 hours. In fact we have recently been searching for a new unrestricted FI, and even offering reasonable salaries, we have experienced difficulties. Bottom line, if you want to move on quickly to airlines, move to a flying school full time where you are almost guaranteed the hours (even in winter). At the moment, I am averaging 60 hours per month(and thats in Scotland!!), however, working for a bigger school last winter, I only averaged 25 hours per month. Bottom line though, because the airlines seem to be taking on lower time pilots, the instructor market is already beginning to show signs of drying up, and if you can wait until summer time, your employer will almost certainly offer you a good salary.
Good luck with your decision.