UK citizens applying for a Chinese visa in Mongolia

Dear Sir/Madam

I've read the answers to the previous questions that states you have to apply in your country of residence, and that it is valid for 3 months from issue date. As we are driving from the UK through China it will take us more than 3 months to get to any Chinese border. Can you please advise how we can go about to apply closer to the border and time.

If you have any advice what will we need to do the trip, it will be greatly appreciated.

Thank you so much

Anton Knoesen