Just read your post and have copied a posting from Yahoo on what should not feed pet rats, if you do not call out Rentokil, it might make sense to leave some of these foods out at night and eradicate the rats this way.
Hope that helps - it has worked for me as I had one living under an enclosed chicken shed and it had eaten its way in, but putting out the cheese has seen an end to it.
Foods NOT to feed to your rat
Blue Cheese - Contains Toxic Mold
Green Bananas - Inhibits starch digestion
Green Potato Skin and Eyes - Contains solanine, a toxin
Licorice - Contains a suspected neurotoxin
Orange Juice - May contain d-limonene which can cause kidney cancer in male rats see also this post
Poppy Seeds - Can cause neurological damage, or may cause death!
Raw Artichokes - Inhibits protein digestion
Raw Bulk Tofu - May contain bacteria (packaged tofu is safe)
Raw Dry Beans or Peanuts - Contain antinutrients, causes red blood cell clumping (note: the peanuts that you buy in stores are almost always roasted so are okay. Frozen beans from veggie mixes are okay because they have been pre-cooked)
Raw Onion - Can lead to anemia and an upset stomach
Raw Red Cabbage and Brussel Sprouts - Contains an antinutrient that destroys thiamin
Raw Sweet Potato - Contains cyanide-forming compounds
Rhubarb - Contains high levels of oxalates which bind up calcium
Wild Insects - May carry parasites
Foods to be used with caution when feeding to your rat
Apples - Apples are fine, except for the seeds. Apple seeds contain a cyanide derivative that is deadly.
Avocados - Avacadoes are high in fat and are a good treat to feed rats that need to gain weight quickly (make sure the fruit is ripe). However, the pit, rind, skin and leaves of avocados are toxic. The part of the fruit in contact with the pit has a higher concentration of toxins.
Carbonated Drinks - Rats Can't Burp!
Chocolate - Contains stimulants that can lead to heart failure or neurological poisoning in high quantities. A very small bit of chocolate is okay and can actually temporarily alleviate respiratory distress.
Dried Corn - Can have high levels of fungal contaminates which can lead to liver cancer. Make sure to inspect commercial seed mixes with dried corn. A little fresh corn is fine.
Iceberg Lettuce - Full of water (which can be good), but has no nutritional value
Peanut Butter - This can cause choking in rats. If you want to give your rats peanut butter, mix it with jam or something liquid to make it less sticky, or spread it in some bread.