If you changed all 4 wheels to a replica brand, you would have to declare it
From Aviva "If your vehicle's alloy wheels were fitted by the manufacturer, they'll be covered and you don't need to tell us about them on your insurance policy. If the alloy wheels were not fitted by the manufacturer, but were fitted later, you must tell us about them on your insurance policy."
I think an 'OEM replica' is much more of a grey area because we're describing the wheels in different terms to other parts. These aren't aftermarket 'upgraded' alloys.
If your shock absorbers needed replacing and you jumped on ECP and were presented with the option to buy Sachs/Bilstein/Monroe or something would you phone up your insurance to declare you'd fitted 'replica shock absorbers' or would you just consider it a normal OEM spec replacement pattern part?