Rocker switch + dimmer switch = UGLY
Buy a 2 gang dimmer and a http://www.tlc-direct.co.uk/Products/VLSM.html...then replace 1 of the dimmer modules with the switch module.
= PRETTY
The dimmer your sparky wants to purchase will be fine for the job.
Take out your existing vpro modules and have them as spare or if you need them when you convert another room to LED.
Dimming the lights on a stairway?.....hmmm....
If you want to dim from both locations you will need an IR master dimmer used in conjunction with a slave.
A good quality LED dimmer can be used with other forms of dimmable lighting.
varilight sell a switch module that is a direct replacement for 1 of the gangs on a 2 gang dimmer....
So, it will look like a 2 gang dimmer but 1 side is a dimmer and 1 side is simply a switch.....