BBC Radio 2 or Magic on 105.4 are the two stations I tend to listen to in this area, and they both give out traffic reports. Not quite so frequent at weekends though.
I used to travel down the M6 from the North west quite frequently, branching off for the M40 and then anti-clockwise around the M25 ie away from the Dartford tunnel and found this generally to be quicker and less congested than clockwise.
Occasionally I would cut across country earlier and pick up the A50 or the A5 over to the A1/M1 and this used to work a treat too.
Bear in mind that at the end of November the toll booths at Dartford will become redundant. This may speed travel through/over the crossing but may encourage more people to take that route due to the lack of perceived congestion at the crossing.
I tend to go for whichever route is shortest. Congestion cannot be predicted unless and until you have heard the traffic reports. I used to use various parts of the M25 when I was working, as I used to travel the country extensively. In my opinion, one of the worst sections for congestion was between junctions 18 and 13 anti-clockwise. Dartford could also be bad, and so could the junction of the M25/M26, but which is worse at any given time is impossible to say. From the M40 I would probably go anti-clockwise, but from the M11, A10, A1M, or M1, I would go via Dartford. It all depends on where you join the northern section.
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