He says "I'm a great believer in learning new stuff" New as in a relay in a circuit, the relay having been with us since 1835!! Seems a nice chap but slightly worrying that he is all foxed by something so achingly simple! I'll add my vote to not going the contactor route - three issues at play: 1: They will hum like mad after a few years, even decent ones. 2: You will add a whole load of extra wiring that you don't need 3: If a chap comes to swap an appliance over and thinks he is making an isolation by flicking the lightswitch controlling the contactor, he is only opening the contactor, which is not a safe method of isolation. What fittings are the customer speccing, Hamilton? Wandsworth? clearly something costly - check fleabay I have had some great deals on fancy fittings on there.
why make the job harder to save them money if they can afford expensive accessories they can afford to pay a tradesman and buy decent materials
It’s not a terrible Idea but surely it wouldn’t be cheaper, bearing in mind you would need a contactor and a switch (still from the expensive range) for each appliance to be switched unless you were going to switch them all off together ? plus the extra enclosure, wiring and labour costs.
No way it can be cheaper, say you are doing 5 appliances, thats 5 contactors, a CU carcase to put them in, runs of 1.0mm to the control switches on top of the power runs, then the light switches from the expensive range plus the labour. Even if the DP isolators in the high end range are £50+ a lump, it won't be cheaper if you are charging the job up correctly.