A few questions in regards to changing a flight destination.

We have two Business class ( I class ) tickets to YVR coming up in October.
These 2 tickets are the return portion of the YVR-LHR ticket we had used in July.

I have recently married and moved from YVR to the UK to live. We don't actually want to fly back to YVR in October. Is there any way we can use the value of our return flights on purchasing a totally new trip? One that will now start and end in London.