Renewal of UK Passport from TRNC

[KibrisLife]

Not sure this is the right section but anyway.....
Needing to renew my passport and will do it via DHL - anyone had any bad experiences?!
Main reason for asking - do they automatically return your old passport with the new? This is really important as we have our resident/work permits in them!
Anyone that has done this all before and can offer info, as reading Guidance notes for the application on government site seems to not utter one work about it.
Many thanks!