I’m guessing 3am is fine, but how bad would 7am be?

Thanks in advance

No, its pot luck from any time after 6:00. Always prepare with a big cup of patience. I go the other way around up to about 270 degree’s, if that makes sense.
Example. A3 to M11, I go Heathrow way around.

Many thanks, that’s pretty much as I suspected

really? I’d take Dartford over the colossal farce that is the Heathrow junction any day.

After 9 most mornings I get straight through.

Currently the roadworks aren’t helping things!

North to south isn’t that bad, just prepare for the worst, but hope for the best!
The other way is a lot worse..

A3 to M11, I go Heathrow way around.

I always thought that Heathrow was the busiest bit?

It’s much better since they put the new numberplate readers in. When I do it I usually get there around 7:30 and there is rarely a queue (but I avoid Mondays).

IMO the M4/M25 and the M3/M25 junctions are worse than the Dartford crossing.

I commute from Bromley to Basildon most days.
Normally expect 10-15 delay at 8am going north however I sat in a quee for 2 hours yesterday!

A3 to M11 isn’t that much different distance wise either way though. Iirc there’s barely any difference at all M3/A12 north vs. South (one junction west /east respectively) either.

In fairness both ways can be disastrous on the wrong day.