I spent some quality time on the M25 last weekend. It wasn’t that busy, even when I came across those roadworks on the northern section which are taking forever (well, until next month). Despite the enforced 50mph limit it really is a very good road that gets you from East to West, North to South and vice versa fairly effectively.
Outside of dull holiday weekends I try to get on and off before 7am. Avoid anything approaching rush hour and stroke my lucky rabbits foot to avoid any tailback dramas. It seems to work. No, the M25 is a good road. A bad road is the North Circular.
If you’ve never driven to North London or don’t live there you may not know it, but I have wasted more hours of life on that road than any other. Despite upgrades and occasional multiples lanes it still bottlenecks and only needs an out of sequence traffic light and you are there for the night.