If your going to get magnets and are sure your going to stick at the business I personally would go with sign writing, properly. For a small van both sides, front and back a local sign writers should do it for about £150 tops. Think it looks more proffesional, and if it is a works van only.
As for how much work it will bring in im not too sure, I wouldnt sday loads, just a few here and there. But recently there are a few people on here that have landed very big contracts due to being seen.
Also only seeing ten people i think is not enough. Stick at it, go out at 5.45-7.45 every evening and throughout saturtday, stick at it and you will get better results than you have had and will succeed.
Good luck!