Dear Customer
All pre-order equipment has been in stock since end of December / beginning of January. Since then we have been contacting every pre-order customer via email to confirm their addresses in order to ship their merchandise. As we cannot store the miners indefinitely, back then we have set a 3 months storage deadline after which we would dispose of customer's equipment.
Dear Black Arrow employee
Once the storage deadline has passed
you should refund the customer in full. They have paid for the equipment. By "disposing" of that equipment (assuming it exists at all) without permission, you are committing either theft (if the miner exists) or fraud (if it does not). Either way, unless a full refund is made you are committing a criminal offence.
You should also bear in mind that some people have invested several thousand US dollars in your product. Some of these may be "Joe Public" buyers, others will be legitimate businesses, and others may (most importantly of all) be organised criminal gangs looking at Bitcoin mining (or at least the purchase of miners and subsequent selling of mined coins) as an easy way to launder money or finance other crime.
Given the amount of people still waiting on their miners, I'm betting at least one customer falls into the latter category. What do you think happens to people who steal from these people? Do you honestly think you can run? Change your name? Change your country? Do you think they won't find you? What if the police catch you first?
Do you honestly think you'll live long enough to stand trial?