Most insurance companies have an option for Manufacturer Alloys/Optional extra alloys which is generally much less of an increase than aftermarket alloys as such.
So basically a VTR running VTS Wheels would barely increase insurance, where as wacking some Lenso's or OZ's on will increase a fair bit (this is dependant on Insurance company though).
If the insurance company doesn't have an option to say that your using optional extra/manufacturer wheels, only one for aftermarket wheels, I PERSONALLY wouldn't bother declaring them unless they were a non-standard colour (eg White or black) rather than just metal. This is only my personal view though.