Mounting a recessed shower valve

[Muzungo]

I'm replacing my shower valve, but the back of the cavity in the (two course brick) wall is uneven. The old 15mm pipework was holding the old Mira 8 in place.
I'm running hep to the new valve, but now I need to put a board at the back of the cavity to hold the new valve. The cavity is about 1 course deep.
Any tips on making sure the mounting board is plumb when I bed it in there ? I'm thinking quick dry cement and a small spirit level.. but any better tips would be greatly appreciated...

 

[ChrisR]

Is sympathy any good? Horrid job because the bits aren't designed properly!
Sometimes you can use 2 backplate elbows to fix things (the fitting you use to hold an outside tap to the wall)

I have used a big blob of car body filler - sets in a minute or three

If you get things where you want you can use builders foam all over, and just let it set. Quite good method, that.

 

[Muzungo]

Is sympathy any good?

Its certainly appreciated
It's a bit of a pig... I can't drill into the back of the hole, because that second course of bricks is what separates me from the neighbours bedroom..
Foam is a good tip - once I've got the thing level.
I'm thinking maybe some 2x4, cut down to the required depth, nailed to a longer piece... use the wall as a guide, press the cut bit in to level some quick drying cement.
Anyone got any better tips ?