It's not an area I'm familiar with - I do electronics more than electrical - but I see lots of people using DIN rail and associated fittings, and that gives a very neat and professional-looking result. Having just bought my first DIN-compatible component (Pilz safety relay cheap off eBay) I'm not sure where the best place to look for all the other bits is. I guess I'm going to want a fair selection of terminal strip connectors and that kind of thing. Googling sometimes turns up too many results - does anyone have a suggested supplier for these kinds of bits?