Traffic round this island has kept to the left for 2,000 years. Although the scything techniques of the Ancient British charioteers do not suggest lane discipline, there is good evidence for it in the contrasting ruts left by Roman carts at a quarry near Swindon.
You should, however, approach the reasons for its continuing sway with caution. Most popular is that it best suited right-handed self-defence.
Continental contrariness is hard to explain, particularly as leftism is safer (dominant right eye, etc). Apparently, Napoleon insisted that people drive on the right in the countries he conquered.
The Dutch, victims of this dirigisme, call the British, a touch enviously, "linksrijers", left-hand drivers.
The anti-colonial Americans did for left supremacy: the ratio now favours the right-siders by about 4:1. The minority comprises the British-connected, including Japan.
Consistency would urge standing on the left on escalators, and a change-over would certainly enliven things for a while.