This has maybe been covered already. Different architects will advise differently I'm sure, but what's the general opinion on insulation in the ingos?

Do you need Kingspan there too? Do you make window frames big enough to take 25mm Kingspan and plasterboard either side then put double fire stops around the windows and doors? Or is there other options? 

In Scotland, the Accredited Details have insulated ingos, we always detail the ingos with them, depending on your window type and manufacturer, you might find that that structural opening doesn't change at all...