If you put an fcu before the socket you dont really need a second fcu just a light switch as the original 13 amp fuse will protect the lighting cable aswell. (By a long way as you plan to use 2.5mm)
It looks ok, you didn't mix up the blues or yellows did you?
The middle switch red, yellow, blue should all be coming from the same cable.
Looking closer, I think you might have mixed the blues up, cant see the red sleeve on the one?
Just treat the 3 switches as 3 triangles, they are the opposite way round on the new switch, just transfer the wires over one by one.
Old- new
L - com
L1 - L1
L2 - L2
The above is correct
Well done for taking a before pic, you're probably gonna need it.