I was pleased to read in this report that in Kings Lynn, Local Authority officials are checking up on HMOs. There is not much point in having laws to legislate HMOs, poor conditions in property, and the like if nothing is done about it.
As was pointed out by Mark P in the comment here (you need to scroll down), many Local Authorities are unable to do anything due to lack of funds, so it is good to see that are taking their responsibilities seriously.
My feeling is that the only way properties owned by the worst landlords are going to be improved for their tenants is via action from Local Authorities. Probably the most effective course of action would be for the LAs to do the repair work themselves and then re-coup the cost from the landlord.
They do actually have the power to do this now, but perhaps for them to use these powers, their right to recoup the cost from the landlord should be beefed up a bit. If landlords feel that they are going to lose their rent for a few months or years, it may persuade them to put their own house in order, so as to avoid it being put in order for them.