Installing window gap

[nordita]

I'm installing a UPVC window but there are gaps up to 30mm since my block work wasn't even.

    10mm
 __________
|          |
| 25mm     | 25mm (30mm from outside just on this side)
|          |
|          |
|__________|
     0mm

Is expanding foam suitable otherwise I was thinking of cutting a wedge of treated timber?

I have some left over upvc soffit materials I can use hide / waterproof the exposed foam/wood edge. On top of this will be more metal roofing sheet I'm using as cladding.

 

[nordita]

I forgot to add. Do I need to use any damp proof membrane / course material if I'm installing it into a single skin block wall?