Home DIY

I suspect that if you are just making it a less awful place to do workshop tinkering or keep a fridge freezer then just insulate away.

Also:

• if you didn't tell them, would they find out?
  
• if done, is it done irrevocably?
  
• do your insurers care?
  
• when you come to sell, would the work significantly contribute to the cost of house, and would the buyer expect BC approval?
  
  

Practically speaking, if its a no to all of the above, not a lot stopping you...