As a wise woman once said to me "nae cheek, nae chance" - what's the worst that could happen? If they find out, you'll be told to move it. They'll not come and demolish it, not without a protracted legal battle, so as long as you move it if/when they tell you to I'd say go for it.
I'd love to live in a tiny house (or yurt) completely off grid, but with 4 kids and a husband all hard wired to the modem and a love of big bouncy dogs, I don't think it's going to happen anytime soon. Good luck
If the council tell you to move it , and you do not in the majority of cases they serve a enforcement notice.
They will give you a period of time to move it
Say 3 - 6 months if its a home allowing time to relocate.
If you do not agree you can appeal the enforcement notice within 30 days.
Then it can drag on for another year or so, if you appeal and its on planning it goes a bit quicker 3-6 months.
But even if you loose you can apply for extension to remove it planning inspectors often allow 9-12 months for relocation.
Thats if you get reported
If its a caravan you need 10 years residential use before a enforcement notice is served
If you say converted a barn and lived in it for 4 years as your home.
In both cases if its proved the use becomes immune from prosecution or forced removal