most comencel (insect that live with man, stord product insects), are brought in via packaging, pot plants, bird nests or make there way in under there power. problems can be sorted out by.
1,remove old stale food and packaging
2,good clean down (the good old vacuum cleaner is a fantastic pest control tool)
3,water based insect killer (ant killer, bug gun, ect) this when applied on clean cervices will be affective for up to a month and once dry is very safe for kids, pets.
4,prevention, start at one corner of the house on hands and knees go all the way around if you can fit your ickle finger in a hole a mouse will get in, three fingers a rat. have a look in the loft, clean out birds nest's. rotate stock yes those old packets of dry food at the back of the cuboard are vermin hotels.
over the next week or two look out for solitary bees ( masonry bees, mining bees) they only live in your outside walls for two or three weeks and they are harmless cant sting please do not kill them. one solitary bee can pollinate as meny plants as one hundred honey bees. watch the program about bees bbc4 Thursday 9pm, bees are important and they are disappearing at an alarming rate.