I'm glad that it's not true about insurers not insuring people with modified cars... I thought that sounded a bit strange!.
What bugs me though is that some modifcations, such as brake pads or suspension... if they are just standard replacements you don't need to contact the insurance company... but if they are something good quality and with a name (not something stock) then they want to know about it.. or at least they do when you look at online quotes...