Interesting question just came up re driving in the UK on Reddit. Someone wants to go from the M11 to the A3 and asks which way round the M25 they should go. These roads are pretty much equidistant regardless of whether you go clockwise or anti-clockwise round London.
That’s the route we take to Scarlet, so I have opinions on this. Go clockwise from the M11 and you encounter the Dartford crossing. This is a toll crossing, and is often very congested.
Go anti-clockwise and you pass the Heathrow section.
For me, there is no contest. Pay the damn toll. It may be annoying to have to put up with the Dartford crossing, but the Heathrow section of the M25 is the very arsehole of hell and to be avoided at all costs.
Interestingly, most commentators felt the same.