I'd agree that you're looking at spending £40-100 on a new wifi router or mesh system to have properly functioning controls, but give it some thought before assuming that technology is the answer. Usually these requests to temporarily block a device involve a child/young adult......If this is "overnight" use, and you don't need access to broadband then, a six quid timer plug on the hub will prevent any internet access via that route outside your chosen hours.
If you want to selectively block their internet access, and to be effective, there's more than just pausing the device on your own broadband - you need to make sure that they also can't access any guest wifi network (potentially including signals from neighbours). If they've got access to the phone, but no broadband, they can possibly still use mobile data. Block or stop that through mobile account controls, and the more enterprising will buy a compatible SIM, or even a cheap second phone which can be had for pocket money cash. Sometimes there's also a content or website aspect (eg adult content, gambling, compulsive gaming), it is worth being aware that getting round most ISP and mobile "web protection" filters is trivially easy for anybody so inclined.
So pausing the wifi access works if you can be sure all those bases are covered. In these cases it is often better to agree a "contract" with the person concerned, about when and what they can do on their phone, along with the consequences of non-compliance, and trying to do this through negotiation and trust. If it is a PAYG phone in your name, then you've got some leverage in the shape of refusing to top-up the phone if the rules are broken, but that's a sanction under the agreement, and shouldn't be put as bluntly as a threat. Perhaps "phone to be on charge in the kitchen/living room from 8pm to 8am" type of agreement? Often by the time people ask this question there's already strained relations over device usage. If that applies, you need to raise the concerns with the individual, explain why you want the new rules, why that's to the benefit of them, and what the sanctions will be, and how long they will last. You need to keep calm, don't get into a shouting match - with your own children it is difficult to avoid this, you need to approach it as a logical behaviour management problem. When they start getting heated (if it is a teenager this is almost inevitable), you leave it, and walk away, and return to the topic another time. If you raise your voice, or utter the words "because I say so" then you've already lost the argument. You might need to change the hub and wifi passwords and block them for 24 hours to "force them to the table", but don't do that before trying to engage, and above all do not getting into an emotion-driven argument. A moody teenager will often throw everything back at you that they can (all the usual stuff about you don't understand me, this is what everybody does these days, all my friends have unlimited internet access, you don't love me etc etc), and in that case it is very difficult not to be drawn in to an argument, but you must not do that, you must avoid laughing at any tantrum.
