Thank you for the helpful answers:)

However, could I ask further about the PSU earthing? This is the PSU which I bought from Zapp ready-made for convenience:

http://www.zappautomation.co.uk/elec...er-supply.html

As you can see, it has no metal case, it all sits on the pcb and I can't see an earth point. Maybe this one has internal earthing, if such a thing exists?

I see you are both using MCB's that's cool, I'll have to investigate this. At the moment, the limit switches (micro type) IO's are fed by the 3.3V supplied by the Kflop board so I don't need additional low DC supply. However, I am going to use proximity sensors instead, and that will require a 24V supply. So as I expand and start to use relays to trigger this and that, I will need an enclosure that allows for this expansion, even though at this stage it may look huge and rather empty.

Another question regarding proximity sensors, I ordered a couple of the cheapo ebay ones for less than 10 quid each to play with, a bit bulky, but are they any good? I notice that some proximity sensors can cost a small fortune. For our type of usage, what does an expensive sensor offer that the cheapo ones lack?

Edward