I too found it strange that the lady turned up on TV in WB ahead of her husband's cortege.
But I suppose there is a simple explanation for this (and others before)
After the C17 bit, they go over the road to the Chaplains place for a period, and it must be at this stage that they have the option of going to Wooty B ahead of the cortege.
Notice that this is not a normal funeral cortege, its seems the only vehicles are the hearses. It is, of course, a repatriation, and delivery to (I think) John Radcliffe Hospital Morgue.