Find out who insures the apartment block. If possible insure with them. Then, if there is a claim, there will be less chance of arguments as to whose policy covers it - either way the same insurer has to pay out.
We got insurance quotes from one direct and eagle star and there was no problem that the property was rented. Ground floor apartments can be more difficult to insure.
I rang around 15 different brokers some months ago and the only ones who did this were [broken link removed]. They were also very polite and helpful, where most brokers were barely civil... give them a call.