Ok my head is hurting a bit but I have read most of this and the linked threads and I think I have narrowed down my choices to two.
Note: Like most here I am in the UK and only have 2-wire circuits.
I would have ideally liked to get the Lutron Caseta which does work with 2-wires and does dimming but the damn Americans have refused to do a version for Europe despite the fact Lutron do other products in Europe and despite the fact it has been out nearly three years. 
The two options that I am looking at are -
- Dumb switches with Fibaro dimmer module
- Possibly the Gen 2 Z-Wave from Carousell as mentioned by @CSC
I do have a few questions about each approach
If I use the Fibaro dimmer module is it compulsory to use a momentary switch rather than a standard on/off switch?
Is there any type of physical switch one can use with Fibaro to also make it dim up and down?
I would like a choice of 1-gang, 2-gang, and 3-gang switches all in a square standard size and matching style, plain white would be preferred.
Am I right in thinking that the Carousell switch will both receive Z-Wave commands to turn lighting circuits on and off, and also provides a physical button for on and off?
Am I right in thinking that the Carousell works with 2-wires and does not need an additional device e.g. dimmer/relay?
If dimming on the switch in either approach is going to be difficult to achieve I am prepared to give up on that and just have on/off.
Am I right in presuming that both approaches will work for both standard single switch e.g. living room, and dual-switch i.e. stairs installations?
Links to UK resellers would be very much appreciated.