VS simply doesn't upgrade because you're newly weds.

Your miles redemption ticket cannot be upgraded with money, only more miles.

If I were you I'd look at the buy miles option - you'll need 20,000 miles to upgrade from PE to UC and that will cost 315 in UK money ... however, LGW-MCO is a difficult route to get UC redemption on due to its popularity and the low number of UC seats on the aircraft that serve that route. And moreover, you're travelling in less than a month.

I'd settle on what you have and not expect that you'll be able to realize your plan unfortunately.

Regarding the clubhouse - again no you won't be able to access this unless you're in Upper Class or have booked through VHolidays and purchased access (actually I'm not sure about that at LGW, perhaps the VRoom???).