Here is a nice link for elderly FT's https://www.gov.uk/state-pension-if-you-retire-abroad/how-to-claim

There's a download on that site for your pensions applications form; fill it in, not forgetting to include British bank details, send it off, lie back and cuddle that ex-student you married. You'll both be able to live like lords in China(if you are careful) on your British state pension. Do the occasional off-the-record teaching, and Bob's you Uncle, Sally's your Aunt-you'll both be laughing your way to the Chinese money machine once a month.