I'm interested in sending a copy of my hard drive (all data encrypted) to be physically stored away from my physical location, as a protection for archived data against loss from local physical dangers. I would be storing simply one external hard drive measuring less than a square foot in size. I'm trying to find a service who would accept and store such a small package as cheaply as possible, receiving it by mail and returning it by mail if requested. It doesn't have to be in any particular country. I'm based in the UK but could send abroad.
How do I use mail storage, and what services provide the cheapest available services for storing very small quantities for long periods?