Declaring modifications to insurers

I have recently replaced my bumpers and alloys in an attempt to replicate a classic version of my car. Now, the stock alloy wheels which are FORD where 14" however I have swapped them out for a set of FORD 16" alloys. The same goes for the body kit, if it can be called that. Again the bumpers have been replaced for another genuine OEM part again which is a FORD part. So in essence all the mods, are not aftermarket but are genuine parts from the "hot hatch" version of the car. Do I need to declare these since these are still OEM parts therefore standard or not? If so would you imagine an increase in premium, I'm declaring my AFTERMARKET steering wheel tomorrow when it's fitted but I'm unsure about these standard parts.

I think you want to declare them, because if you are in an accident, you want those parts replaced with what you have, not what it came with. I can't see any appreciable increase in premiums. Insurance companies use any excuse they can to save a buck.

You have to tell your insurance if it does not match the spec for the vin number. Some will not charge more most will and some will not cover you. You should have talked to your insurance before spending you cash.
When I had an accident not my fault the other party paid in full the insurance still checked for undeclared modifications as a way of getting out of paying.
My car is stock so no way out there.
Nor declaring them can leave you uninsured.

You have to declare these things because they make it more likely the car will be stolen If you don't then if there's a claim they will weasel out of paying.