what are the chances of a honeymoon couple who are flying club members and frequent virgin club members getting a free upgrade on what i would call a reasonably empty flight? :X :X
Honestly, very little to absolutely none.
Firstly airlines only upgrade people if they *need* to, because the flight is oversold and they have to move people, a quiet flight is not good for op-ups. Then it will be done in a specific order, with gold card holders been at the top of the list, followed most likely by single travellers on full fares.
The notion that the fact it is your honeymoon will have any impact is an unfounded rumour.
Sorry if it sounds harsh, but better to be realistic than have false hope.