I don't know how Exec will run their business, but typically in the UK an agency will supply a cleaner for you, who is typically a housewife or similar with time on their hands and wants to earn some extra money. If you're happy with the cleaner they supply, they end up working regularly at your house, for months or years.

All this time, the agency is taking a % cut for providing the original cleaner. After that, the additional value they add is zero.

So yes, it may be unethical to disintermediate the agency, but by this time you have been working with the cleaner for weeks/months, so you get a fairly good idea as to what sort of person they are.