After a detour while getting dinner, I can confirm there are now two SIS vans in the compound. One buried in the middle which did use to have it's dish raised, and another parked up at one of the access points on the road, which would suggest to me something on the van died.
Here's a couple of photos :-
First, here's the original van, hidden behind the scaff tower with the big dish on (I believe this is the Eurosport uplink, with SIS providing the BBC feed - this is because this is the way it used to be done with BT doing the BBC job). The little van I believe is for social media type streaming feeds etc. This stuff is at the opposite end of the compound to the fibre wallbox.
From round the corner and the other end, you can just about see the dish of the second SIS van. A second uplink van normally appears here for the final weekend anyway, and it's an easy place to get the van inside the fence.
In the BT days, BT would fibre the feeds back, with their van parked almost where the second SIS van has appeared today, which is adjacent to the fibre wallbox. They would then add a sat truck for the final.
I don't know that SIS aren't using the fibre, but my suspicion is that they're not.
Back to work!