VOA or Chinese Entry permit

I am writing to inquire about the entry requirements for visiting Shenzhen from Hong Kong.

I am a UK citizen with a valid UK passport, and I plan to visit Hong Kong before travelling to Shenzhen for a maximum of 7 days. Could you please confirm whether I need to obtain a Chinese entry permit in advance, or if I can get a Visa on Arrival (VOA) at one of the Shenzhen entry points such as Luohu Port or Huanggang Port?

Additionally, could you please advise on the necessary documents I would need to bring with me to apply for a VOA?

Thank you very much