Perhaps I shouldn't have said anything. I really have no idea. Very sorry John.
It all depends on the traffic conditions on the day.
The only reason I mentioned it is because the Embassy in these days is really not understanding about missed appoinments.
Sorry if my comment spooked you.
It's a little bit like the drive to Heathrow from my place. Should be 2 hours easy, but often given the M1, M25 and M4 conditions who knows.
Depending on timing etc I'd rather stay overnight at an airport hotel just to be double sure.
I don't know if it's possible for you to find a hotel room a little closer?
I do apologise John, I'm sure you know it's impossible to predict travel conditions.
But maybe you can find a hotel somewhere closer to the Embassy??
Just a suggestion from a worried observer.