My dh and I drove over 500 miles yesterday, from London to NE Scotland. I drove non-stop from SW London to Charnock Richard on the M6, about 200 miles, via M25/40/42/6.
I find the M25 is actually quite disciplined with traffic management in place, far better than previously, when people used to belt long. I don't really care whether people lane-hop, so long as they don't endanger me! I've never not been able to get onto a motorway from a slip road; Ime, if you indicate, people will in general move over or flash to show they're slowing down for you. I do like getting north of the Lakes area, though, where the roads are much clearer!
This Autumn I was lucky enough to get a new car and I went for an automatic, after driving dh's auto. I absolutely adore it and would recommend one. The modern autos are so much better than those of old, mine has eight auto gears plus it can be driven in manual, if you wish, such as on the challenging mountain roads where I live.
In answer to the OP, though, definitely get some top-up lessons. It will restore your confidence and you'll feel ready to roll again!
How will things change if our summers keep getting hotter


