Not sure. I've always just used Neosorexa Gold. You need to find the access point and block it up today. It might be worth lifting the floorboard where you suspect the rat is if that's at all possible. Poison should be laid in rat runs, they will take time to take it and then take time to die, so I'd also set traps baited with peanut butter, as if it's just happened you might catch the lot. How awful! We have masses of rats right now too but all under the chickens sheds -I must get busy with the Neo Gold too.
Our neighbours had the rat man in recently for their chickens on our boundary. Chickens now moved and rats gone but he did say that once you've set up the poison, don't go moving it around. Rats like familiarity and any change will put them off. Also wear gloves with anything you touch relating to the rats. This isn't just because of the toxins involved. Rats have a great sense of smell so if you touch anything you use with bare hands, they will know and steer clear. It took several weeks to clear the whole big nest because you will always see far fewer than there actually are . Unless you have quick success (and that takes a while to be sure about) I would call someone in when it involves rats because the poisons they use are far more powerful than what you can get in the likes of B&Q. Our neigbours called in a local private guy (accredited) but I would guess the council contract out anyway.