Why it is non-negotiable

You are creating new habitable space, altering structure, and changing the fire strategy of the whole home. All three engage the Building Regulations directly.

What about 'just a storage loft'?

Boarding a loft for storage is not regulated. The moment it becomes habitable — lighting circuits, heating, regular access — it is.

Doing it without approval

Unauthorised loft conversions show up at resale, on mortgage applications, and on insurance claims. The fix is a Regularisation application, which is expensive and intrusive.