Insulating cavity below bay window

[mistake_not]

In my renovation I have ripped off the window sill around my bay window and exposed the cavity underneath. It's had some failing glass foam insulation in it, so have emptied it all out. For context the wall is a traditional brick and block build, with the window sat on the outer brick leaf. I will seal to the window with insulation and air tightness, but am unsure what to re-fill the cavity with 

 

The cavity varies in size between 60 and 35mm, would seem obvious to use EPS beads. I thought maybe use an old bin to mix the beads and PVA and then out them in? Anyone got any experience or better ideas?

 

It's only 1m high, and about 2m along.

[Mr Punter]

I don't think the adhesive is critical for this.  Just pour the beads in.