Steel over sliding doors cold bridging

[Mattg4321]

Appreciate that this has likely been done to death but I’m struggling to find something totally relevant. 
 

Steel I beam with 10mm welded plate to the bottom to take the outer brickwork (2 storey extension). 
 

The detail supplied by the company installing the doors shows timber sitting on the steel plate in the cavity, but I’m not convinced this is the best way of dealing with this. 
 

Anyone?

 

 

[Mattg4321]

Forgot to add that this diagram doesn’t show the cavity tray that I’m sure will be required, and how that will stop the insulation above the steel?