Mr.Oldroyd, please don't worry, you don't have problem for obtaining the China visa again, you can enter China in the very near future. On the visa application form, I don't read that there are itmes for overstay, you can explain the reason and situation on the Section 5 of the visa application form if you want. It is not a big problem, the immigration officer didn't ask to pay for fine and issue you a new visa to leave in 10 days.