If you were fitting aftermarket 19's then I suspect your insurance company might want to know, but for factory fit/OEM 19's then I don't think you have to disclose anything. I've also heard it rumoured that if you swap out your RFTs for non-RFTs then this should be disclosed but I don't know how much truth there is in that.
On my E81 I had a custom remap done and I disclosed that to the insurers. They landed me with a £52 hike in the premium over a year - reckoned that was actually good value considering how much the remap improved the car
