For a single domestic dwelling the FSO does not apply, but if the occupier employs a contractor, (cleaner, plumber) the house is now is their workplace, but because the contractor is unlikely to have control, he/she is not the RP, consequently no FRA, but I think the contractor does have a duty of care.
However the problem arises when the owner or occupier does have control and uses part of a single private dwelling for non-domestic use. It then could be argued it does come under the FSO, but it seems to depend on the purpose it is used for and the degree of use. A small office doesn't but a B&B does.
It could be argued that the cleaner's employer (NHS) does have control, therefore is the RP and should conduct a FRA. However because it?s a low hazard situation a FRA would not be required, because in other domestic premises it would also not apply? It appears it depends on risk hazard, a cleaner, daytime risk, low hazard, and a B&B night-time risk, high hazard.