My suggestion would be to make a 'sand bath' from Fullers earth, and to dust all areas with earth too. This usually does the trick. I have not found any to buy here, but it is easily avaialble in the UK. It is also known as Diatomaceous Earth, it is an organic product and is formed from millions of microscopic one-cell algae called diatoms. It normally sorts out the problem within 36 hours. It is safe to continue eating the eggs during and after treatment. It can also kill fleas and ticks on dogs and all other animals, as well as bed bugs etc.

In Spanish it is called tierra de diatomeas so might be worth asking at he place you get your feed from.

Thank you both for your help. I will try to get some tomorrow