How can I "extend" the end of my work visa for an extra month? Tourist L-visa?

I have been working in Beijing for 4 years and I am leaving to return to the UK this summer. My work visa/residence permit expires on 13th July, but I want a few more weeks to travel, pack up and then leave. What should I apply for? An L-visa? Do I need to do this in BJ or Hong Kong?

Thanks all