People really need to start reading their insurance policy documents before they start stating that factory fitted options do/do not need to be declared. Some companies want them declared, some companies don't, either read their policy or ring them up and ask.
The reason some want them to be declared is that they base their quote on the STANDARD SPECIFICATION, if you start putting in sat navs, different alloys or parking sensors they then become NOT STANDARD. Most insurance companies will not charge you extra, but they will also not cover them without knowing about them. The insurers do not have access to a database with information about all the optional extras on your car.
Admiral for example want you to declare ANYTHING that isn't standard spec, including factory fitted extras. They WILL cover optional extras, and they didn't charge me a fee for the sat nav/bluetooth, but did charge for the parking sensors (£30, I tried to argue that they were a safety feature, but they said they're more expensive to replace). In the event of a crash, I will have my bumper replaced like for like, WITH parking sensors. If I HADN'T declared them, I would have been given a standard bumper instead.
I know that from other people, Direct Line and Aviva do not want factory fitted extras declared, but you have to check the policy wording or ask them to be sure.
*EDIT*
Here is the quote from the Admiral Policy Document
Basically, that means, we will not cover any aftermarket modifications, but you have to tell us about them or your insurance is invalid. If you do tell us about aftermarket modifications, we will only replace them with standard parts, and not like for like. If you have manufacturer fitted options, we will cover them, as long as you tell us about them. If you don't, they won't be replaced like for like, and we will use standard manufacturer parts instead.