Wood glue

They tend to use expanding PU foam rather than PU wood glue (that also foams a little bit where not constrained - but nothing like a traditional "expanding foam".

But only the cowboys use foam *instead* of screw fixings

Not convinced that is true necessarily. Depending on the position of the window within the reveal, there may be nothing of merit into which you can drive a screw. For example on many modern cavity wall designs, they specify a "cavity closer" for use at the window reveals to avoid cold bridging. Many of these are nothing more than a block of insulation stuck onto a thin uPVC profile, that plugs into the gap between the leaves of the wall.

Foam in those cases will make a good fixing. The frame will then usually be further constrained the the PB/plaster on the inside, and render around the reveal on the outside.

Yep. Most new bu8ild windows are just foam, unless its a timber farmed place, and even then...

Just as silicone alone is fine to hold down a bog pan

Indeed.

My 1976 semi uses facing bricks that have a frog but are only finished on two faces. This is fine if they are always frog-up but around the window reveals one side has to be frog-down, so this means a massive space under the brick.

In order to prevent the thick bitumen vertical dpc from pushing the bricks out of plumb before the mortar sets, the brickies bashed off the inner corner. Trying to get a conventional frame anchor into this mangled brick with a huge hollow space where the inverted frog is, is a nightmare for window fitter.

The cavity closer was just bits of the inner leaf block which also has vertical holes right through (which makes chasing out electrical channels internally a right royal pain). The concrete mix used to make them semed to have a lot of straw in it so concrete screws just don't seem to be able to cut a thread.

The old closure method which was to turn a brick across the cavity but stop short of the other leaf by 1/2" with some DPC, was IMO a much better method and was used in my house. We worry about trvial minor cold bridging at the expense of structure too much.

Mine uses L-shaped blocks from the inner leaf to form the reveal. Where I replaced a door and adjacent window with a patio door I did use a pvc+foam cavity closer, but the frame still screwed into the outer brick leaf.

I can see (e.g. in Scotland where they tend to set the windows back further into the reveal) there might be nowhere decent to fix the windows into with screws, as the frame would tend to align with the cavity.