Greenhouse insulation

I've never bothered with insulating the gh over winter in the past, and I'm not altogether sure I will in the future, but wondered if anyone else does.

In the recent cold spring nights, like everyone else, I've been covering the staging and ground level plants with fleece and as I had some fat 1" bubble leftover packaging I used this as insulation against the glass where I had tenders.  I was wondering whether to invest in some proper bubblewrap insulation and if so which size bubbles are best, big or small.  To be any benefit does the whole area of glass (roof and walls) need doing?  I have no doubt there are calculations of heat coefficients etc, but I'll go with gut feelings in the end
Any ideas or thoughts?

The problem is that in the winter months, plants need as much light as they can get. To me its a bit of a trade off, less light for slightly higher temperature.

Quite agree Vinny, the main reason I've resisted in the past. At least with covering/uncovering manually the light is only obscured temporarily. I've sometimes used bubblewrap placed over the fleece as an added insulatin layer, which I will probably continue doing. I had hoped we would be putting the fleece, etc away by now.

I agree with you both I’ve been closing up the poly tunnel very evening and putting fleece over my young and susceptible plants. Last night I covered all my toms, gherkins peppers and chillies that were close to the side walls, I didn’t cover the toms in the centre raised beds as I thought they were positioned ok, however some of the top leaves have a bit of curl in them but the bottom ones look ok. I gave them a seaweed misting feed and a liquid feed. Hopefully they will recover. I will cover them tonight