Here are the locations of the extra legroom seats in all the aircraft.
Yours will be either in the LGW 747s or the 330. There are two configurations for the LGW 747s and if you look at the seat map on the Manage my Booking page of the VS website you should be able to discern which one it is. If you look at the small economy cabin directly behind the downstairs PE area and it had two rows it is Config 1, with 3 rows it's Config 2
Config 1 is VLIP/VROM/VROY/VGAL/VROS
Config 2 is VAST/VXLG/VTOP