No, you can’t save £30 per year by switching off your “standby” devices
Strange, I've had a very different experience to the author of this, I've actually got a similar spreadsheet I may clean-up and post to show another view point, however in summary.A couple of months ago I went on a little mission around the house testing the power consumption of devices on standby, as I noticed through my energy monitor that idle power consumption was about 0.4-0.5kW while everyone was sleeping at night, which seemed high to my research of national averages.To my surprise a number of fairly modern devices I found to have utterly terrible standby power consumption, the new buttonless electric hob in my kitchen, the two monitors for my PC on standby, the TV & Blu-ray player and an Aircon unit just to name a few.Since then I used a few Sonoff relays around the house to add these to Alexa, the results were actually quite amazing really, about £10 per week of electricity saved, so £30-£40 per month...So in short, if your similar to me you can actually save £300 a year, I think the key take away here is clamp/monitor your own devices and take a judgement from there, no one house/setup is the same.---Edit, here's a very quick screenshot of the spreadsheet and data I've got to hand at the moment, in time I'll get something better cleaned up and together.https://imgur.com/a/l4xMwbo