can i send my visa application to UK chinese embassy office whilst I am not in the UK ?

You can't send your visa application to UK Chinese embassy office whilst I am not in the UK. Even though you are in UK, China embassy in London and China consulate in Manchester don't accept visa application by mail.

Chinese Visa Application service Center in London and Manchester accept China visa application from ordinary passport holders. If you hold diplomatic/service/official passports, you can submit visa application to China embassy or consulate directly.

If you are not in UK, it is illegal to mail passport internationally. The passport has the entry record of a country, but it doesn't have the exit record of a country, which can reveal that you still in that country.

Thats not correct - the website clearly states postal applications are accepted. The part im unsure was is the sending from abroad.