Typo...

Assume perfectly insulated floor, ceiling & windows.
- Uninsulated - 579W = 7p/hr cost
- Insulated - 168W = 2p/hr cost

Assume 100 day winter, 2hrs/day
- Uninsulated = £14 cost
- Insulated = £4 cost

Assume 100 day winter, 8hrs/day
- Uninsulated = £64 cost
- Insulated = £16 cost

The reality is uninsulated will not have perfectly insulated floor,
ceiling & windows.
- 2hrs/day becomes £42 v £12 insulated
- 8hrs/day becomes £192 v £48 insulated

Typical figures re wall 30% of heat loss, uninsulated floor/ceiling/
window and insulated floor/ceiling/window to equivalent of 50mm
celotex. It comes down to how often it is used (2hrs/day or 8hrs/day)
and whether frost protection is required (which really costs with
uninsulated).
Assuming walls are roughly 30% of heat loss and insulated example
copies the 50mm celotex (or equivalent).