It must be really worrying for you Poppy - especially with young children at home.
Personally, I think you have to hit them hard - poison - put it down overnight when you know the children & any pets cannot get into the kitchen (put a temporary lock/out-of-reach catch on the door). They will take it back to the nest & eradicate the entire family.
Don't bother with the stuff from the DIY stores - I think they've built-up tolerance for it, as it won't work here. We get the powerful stuff off EBAY - Roban & Neosorexa Gold & put it in a Rentokill Tube Feeder - which keeps it in the right place (also bought via EBAY).
Then try & block-off any entrances you can find to stop the little bu**ers from coming back in - don't use foam filler, they will chew through it in 1 night (speaking from experience here

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Once you've got them out of the house, you could then use the Tube Feeder where you store your feedstuff (if you can ensure the children & stock can't get to it).
We were over-run last winter, not wanting to use poison. But we've bitten the bullet, so to speak & we've kept on top of it this year with poison & have bought 2 farm-bred kittens in the hope that we will be able to control the rats again "organically" in the future.
Good luck