which country to I apply the visa to visit china? Portugal or London?

Hello , I'm traveling to China in September I currently live in the UK but my nationality is portuguese ( and so is my passport). I'm travelling from London to Beijing in which country to I apply the visa to visit china? Portugal or London?

Another question I will only be staying in China for 4 days and then I am travelling to South Korea and a few more countries is it possible for me to ask for a 30 days Chinese visa ( as I will be entering from China and then leaving again from China)

Thanks

Anne