UK PO boxes are very expensive, costing over 120 pounds a year more than their American counterpart. Below I am listing my technique to utilising Ebay's Click & Collect service, costing a little effort and a few quid.
First create an Ebay account and Paypal Account
This Is going to be the 'seller account'. Set it up on Tor. For your registration info use a fake Tor based email, a cheap pay-as-you-go phone number, a fake name and a password that isn't connected to you. Basically, don't connect the account to your or your address. This is very important as a slip up destroys your innocence if anything goes wrong.Make your first listing on the account
Put a listing on the 'seller account'. The item needs to be: cheap, something you don't own but would be interested in buying, Buy-It-Now with collect at Argos enabled. Give the item obscure search terms so someone else doesn't accidental purchase it.Buying the item from your regular Ebay account
Sign in to your personal Ebay account from a normal browser and purchase the item choosing to click-and-collect at your closest Argos. Use your credit card and your personal info.Now connect through tor to the Ebay 'seller account'
Accept the purchase. Don't transfer the funds to anything connected to you, leave them in the Paypal to buy bitcoins in the future. Soon you will have the Argos delivery address with a personal number needed to pick the item up in store. Copy this address to clipboard.Go to a market and buy whatever you want
For your address paste the address copied to your clipboard.Collect the Order
Go to the Argos, collect the item with the form that was send to your regular email after you made the purchase.Enjoy your new, cheap PO box!
this would be promising, but ill wait for BBMC to chime in and tell us why this is a ridiculously stupid idea and how they had this idea in the 70s but then the police were done with the hippies and thats why argos doesn't have any goods on the shop floor. or something