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I had to call in a professional. They are extremely difficult to get rid of but your man told me that he does at least 2 calls a day EVERY day from May to September so its a very common problem but people are too embarrassed to mention it.
He sprayed around the skirting board and every window, door etc in the house with a spray. It seemed to work.
The only thing is that ants are not disease carriers and don't cause a mess.
HOWEVER, you need to realise that they come in because they have found a food source. You need to ensure that you clean up everything always......a few crumbs left behind that doesn't seem much will attract them in.