I really might be BU but I don't have enough experience in this area to know if I am or not!
I have cleaners (agency) once a fortnight, 2 cleaners for 1.5 hours, ie 3 man hours. I have 5 bedrooms, 1.5 bathrooms and one reception room. The 3 hours was how long the agency decided it would take. Having never actually cleaned my house from top to bottom I had no idea how long it would take 
I have OCD am quite minimalist and tidy so the surfaces are always clear. There's no tidying for them to do, or ironing, though I do ask that they change my bed. It's mostly just a case of hoovering and dusting.
Lately I have come back to find obvious things not done.
I have raised this issue wih the agency before and asked if the problem is that they need more time. They say no, 3 hours is fine for a thorough clean. Manager of agency seemed to think anything being missed was unacceptable and last time offered me a partial refund or to get the cleaners to come back and do the bits they'd missed. I don't want to be a slave driver but I don't want to be taken for a ride either.
Other relevant info may be that I pay £13ph and I have on more than one occasion come back from work early to find they have gone without staying all the time they are paid to do.
I have guests this evening and am a bit cheesed off to find I will have to get the vacuum cleaner and duster out myself as the stuff that's missed is so glaringly obvious. I am tempted to call the agency and say stick it, I'm going elsewhere.
But AIBU?