For clarity: When you lease a car through the Motability scheme the V5C is issued in your name but sent to Motability.
So the original S172 request would have gone to Motability and they would have given the details that were provided to the dealer at the time of signing the agreement. As such, the OP will likely have received the second S172 request, so the 14 day limit doesn't apply.
If your contact details change, you can update them on the Motability website or by phone.