Apologies for the late reply. Using the chat function was surprisingly easy. As I knew which flights I wanted to rebook with the voucher, I made a screenshot which I provided to the person I was 'chatting' to. as an attachment jpg file. It just saves a lot of faffing if one has an idea which flights you want prior to chatting.

Essentially, one clicks on the 'chat' icon on the bottom right of the screen. The bot goes through some standard questions first of all (Do you want to rebook using a travel voucher, etc. Once you have confirmed you do, then a person comes online, and they sort out the booking.

I had the additional issue that the travel voucher Virgin had issued to me, did not cover the full cost of the flight I had originally booked; they had forgot to include my upgrade which came to just under £1k more than the voucher!. It was all sorted, and as prices have obviously now increased since travel is picking up, I ended up paying an additional £500 but was willing to pay that bit extra as it's long haul LHR JNB.