Not too long ago now, arch-debunking website Snopes posted a great article on the nonsense that’s peddled by museum and heritage site employees;
http://www.snopes.com/2016/01/07/museum-piece/
These traditional stories and myths are a particular fascination of mine, from the joke that became the origin story of ‘Humpty Dumpty’, to the much more famous Tower of London ravens. I have a fair bit of experience as a tour guide myself, and have had to edit or even throw away scripts I’ve been given. A friend and I have come up with a little game called ‘Hence the Expression’, in which we dream up the most ludicrous and/or amusing stories possible about a site we happen to be visiting. As well as sharing the article, I thought I’d also tell my own favourite story of museum/heritage site BS.
I was on a museum staff trip to a historic house in Scotland a few years ago, and we were subjected to several of these dubious stories on the guided tour. One story had clearly been invented by the guides to explain something that they had no information about; the dining table in the main hall. This table had a removable/reversible top, and the story went that in medieval times, diners would flip the table top when they’d finished a course, to allow the dogs to clean it for them. This is so patently ridiculous that if I hadn’t had it earnestly relayed to me in person by the guide, I would assume it was a joke. But my favourite was the guide’s explanation for the old saying ‘lock, stock, and barrel’. This is one of the few sayings that actually has a really well documented origin, but this guy was trying to convince us that it originated with the Olden Days ™ practice of removing the expensive door lock from one’s property and installing it in the door of the new property. I was stunned by this. Not only had I never heard this claim, I’d never heard of the idea of moving locks between buildings. Even on the face of it, this made little sense, and there was awkward silence from our group. I was wondering how to respond to this, if at all, when my boss at the time loudly remarked ‘NAAAAH!’. I actually felt bad for the guide as we all tried hard not to laugh. But it was instructive in terms of how myths come about even in a world where we can find out the correct answer with a few minutes on Google. Imagine how prevalent myth-making was before the printed word!
The BS Historian 
Actually, I rather think that door locks might sometimes have been seen as assets which could be removed and used elsewhere. I have just been looking at an early 17th century inventory of a castle, by then pretty dilapidated, in which the locks are all specifically noted, and their availability for re-use would be a plausible reason (not that I am supporting the clearly wrong ‘lock, stock’ story).
As to your main theme: I have several times heard tour guides attribute the destruction of various monastic sites to Oliver Cromwell. One would have hoped that the popularity of Hilary Mantel’s recent work might have taught them not to confuse their Cromwells.
Oh I don’t disagree that locks would have been reused. It was the idea that locks would be removed as a matter of course that struck me as absurd. If you owned the property, and were moving to another with lesser door locks, then perhaps.