We had here a tube put next to the box for that specific reason - so that things like magazine subscriptions wouldn't get mangled in the rather smaller letterbox. I think it is therefore utterly extraordinary that they sometimes fail to place it in the tube and instead opt for the more difficult, time-consuming and overall mystifying option of squashing the siht out of it, forcing into the letterbox. It's impossible to actually miss the tube as it extends out further than the letterbox and is also literally glued right next to the box in order to clearly define it as a mail-receiving piece of hardware.
I have come to the conclusion that the average postie is perhaps not overly qualified, and a disturbng amount obviously did not take the time to attend the class in which the different types of home postal boxes were defined and so they are therefore ill-equipped to recognise anything other than a square, brick formation with a small slit with the words 'Letters' above it. Time constraints and perhaps further wagging of postie classes means that they also cannot comprehend the notion of driving their motor-bike a few metres north of the letterbox and simply placing it on the ledge at the front door, it did happen once but it was so infrequent and unexpected that it was passed off as an hallucination for some weeks afterwards.
In summary, if you want a pristine, clean, unsoiled copy then yes, your best bet is the Newsagency. But if you want a mostly clean copy and get it quite a bit earlier, the sub is always the way to go. I like the subscription risk simply because I am something of a gambling man firstly and secondly there's no way I can wait 4-6 more weeks for it to arrive on shelves - I'm simply not that patient a man.