When I’ve done HH to Ace, as dull as it is, I’ve always done the M25 -> M/A40. You’re always moving unless you are adverse to filtering through the traffic. Even with the variable speed limits on the M25, especially around junctions, you still make progress.
The city has gone mad in this heat. I was out a couple hours ago - there’s nothing but traffic jams everywhere you go, but it wasn’t as bad as I expected so if you’re up for some filtering going through the city is an option.
I would be tempted to leave the M25 at J9 then A244 through Oxshott to Esher A307/A309/A308 over Hampton Court Bridge then A311 to A312 in Hampton until you hit the A40.
A307/A309 can get congested at busy times if so use the parallel B3379.