Blatant False Advertising

We have the Rain 5G Home premium and over the course of the last couple of months, the speed has continuously worse and worse, to such an extent that during peak times we're lucky if we get a 1Mbps download speed, even though they advertise "ultra fast 5g speeds". It's definitely not an issue with our connection since at 3am in the morning we're able to get speeds of up to 200Mbps, which constantly degrades during the day until it becomes unusable during peak times. Clearly they are advertising a product that they can not deliver and the next step is to take them to the Advertising Standard Authority like other customers did