So obviously UK mail is protected from unwarranted searches similarly to the US. Except ours is protected by statutes and human rights rather than the 4th-A.
We also know that even though the privacy of your mail is protected by these laws, some private and third party companies Terms and Conditions overwrite this if they suspect you violate the T's&C's. e.g. XpressPost, DHL, Evri etc
(We also know they comply when LE says "jump").
If you're in a situation with no fixed address, move around a lot or are trying to keep your address private and detached from where your mail gets sent, what is the best alternative? What PO box? Virtual address for parcels? Or other setup? Which companies are the most privacy oriented and least likely to give up your information? Does anyone have any experience with such setups?