Hi,i know nothing about domestic cleaning,
i mainly offer carpet cleaning,but here's what i would do.
When ever i come across problems like this,
i add it to my terms & conditions.
Write up some terms & conditions or some sort of mini contract
if you have none.State in the t&t/contact exactly what services they are getting for there money, ie if there is any building work,DIY or professional the mess left behind is not included for general domestic cleaning.If they want it cleaning,an extra charge will be applied as it is classed as a builders clean.This will be easy to apply to new customers but what about your current regular customers.....,well i would say to your current customers that you have just updated your terms and conditions due to new government regulations and ask them to sign them.I hope this is some help.