I have noticed that the subscription company which supplies my YM and PBO uses postal services in different countries according to where they can find the best rate each month. YM has just arrived at my home in Dublin with a return address at a company called Air Business, P.O. Box 99900, Dublin2.
Now,as it happens, if I want to buy something online in the UK and take advantage of free UK postage I have it sent to Air Business in Hatfield, from whence it is sent on to my local P.O. where I can pick it up for a fee of €3.45 plus whatever customs fee accrues,usually 23% VAT.