But having spoken to an insurance broker (and one that is quite experienced in this type of insurance) I was never able to have explained to me how its determined the extra premium amount.
Maybe I’m being naive but I would have thought you’d ask insurers to quote with the strip club included, and then a hypothetical figure if it wasn’t. You might even say there is a plan to change the strip club to a health spa (or something) and ask for a quote on that basis. Or ask a friendly insurance broker to do the sums for you.
It should be well worth the hassle because (as Kaindub says) the law allows you to charge owners higher levies if the activities in their lot result in a higher insurance premium.