Correct me if i'm wrong but i thought that with aeroboard cavity insulation that the board went tight to the inner leaf with toggle on wall tie. This, if tight should leave 40mm gap between aeroboard and outer leaf, which is the area i'd like to have filled.
The "toggle" I think you are referring to may serve two functions.
#1. The earliest designs of cavity wall ties, either twist or butterfly, has a point in the middle to allow water to drip from in order to prevent migration of moisture from the wet outer leaf to the dry inner leaf.
"Snots" of mortar landing on the wall tie often caused spots of damp on otherwise perfect niner leaves.
#2. As the depth of insulation became deeper, going from 40mm to 60mm, the toggles started appearing, and to me some of the designs seemed to sacrifice their "drip" function for use as a restraint to keep teh cavity insulation pressed against the inner leaf.
In relation to the volume you hope to insualte, bear this in mind:
You need to check whether this combined insulation will cause problems.
The cavity fill insulation may be designed to work alone and bond to form a mass in the cavity that prevents teh passage of moisture.
Its important to understand how this works and back to the agrément certificate you go
If in doubt, contact the manufacturer and ask him for a list of buildings using his product.
Visit the buildings and ask the users thereof how the product holds up in use.
Ask them if there are any dark patches on walls suggesting mould at cold bridges where the cavity isn't filled properly.
Ask them if there aer any damp patches on the plaster or any unusual smells, suggesting water may be migrating across.
There is no easy way to do this, BTW.
You need to do research specific to the product you hope to use.
Do not accept comments at face value which may be about generic but not exactly similar products.
You'd be surprised how much time can go into product research on a new build or refurbishment if you're using new products.
HTH
ONQ.