Do some checking on the spec sheets and work out the clearance needed.
My electrician can supply 35mm metal back boxes to allow more cable slack and I believe the RJ45 modules are 32.85mm deep (according to
the spec) but they will sit somewhat proud of the faceplate and so might only protrude about 25-28mm into the backbox so hopefully the modules aren't too deep for the faceplate/box combo.
The salesperson at Comms Express assured me that the faceplates and modules would fit into a 32mm surface-mounted back box, but then they would say that
BTW, I found this
very useful guide on cat5 wiring which I'll be referring to throughout the wiring project.
Thanks to everyone for their advice and feedback so far, I'll let you know when the network is up and running and will hopefully be contributing more to this forum in future.