Hi Tom
Just wondering as a starter what is involved in your void cleans. This is because some local authorities require just a clean, some cleaning & clearance i.e. household furniture etc., some paint & Dec's after clean & clearance
Typical instructions could be:
House or Maisonette: Clear out, remove all rubbish, Carpets, furniture, etc to tip, wash, scrub, floors, woodwork and all surfaces, dry.
In the above example this only relates to cleaning but various cleaning tasks then you would need additional costs for clearance and removing goods to a landfill site and associated costs, carpet cleaning etc.,