ive done mine this way since i started, i still have a house. Couldnt you put an RCD on it if you are worried?
I think you need to be well below the timers stated maximum as you get a surge when you first fire the bulb up. Also ballasts are inefficient aswel, so the actual usuage will be more. I got some heavy duty timers. Max - 1,000W iirc, never misssed a beat.