What steps should I take before sending personal documentation to the DVLA through the mail?

Hi people, I’m currently trying to apply for my provisional license without photo ID which has been a total nightmare to deal with so far. I’m planning mailing my D1 form, birth certificate, Passport-style photo, and NIN through the mail to the DVLA in Swansea to have my information checked out. I am curious to know what personal steps I should be taking before sending important official copy’s of my documents through the mail via post office, do they offer any specific services at post offices to help protect your documents when in transit that I should ask for before sending off the letter or will I be all good just slapping a stamp on there and calling it a day. Thank you all in advance, this is coming from someone who clearly doesn’t get out enough and should take it as a sign 😂.