Pedestrians are expected to have common sense
In England and Wales it is legal to cross all roads except motorways (where pedestrians and slow vehicles are not permitted). The Highway Code contains additional rules for crossing a road safely, but these are recommendations and not legally enforceable, although as with other advisory parts of the Highway Code compliance or otherwise can be used to establish liability in civil law proceedings such as insurance claims. The term “jaywalking” is little used and not very well known.
The Highway Code specifically mentions the special case of a car turning into a road which a pedestrian is already crossing; by default, the pedestrian has priority.
In UK schools children are taught to cross roads safely through the Green Cross Code. British children are taught to “Stop, Look, Listen and Think”, before crossing a road.
In Northern Ireland jaywalking can be charged at police discretion and usually only in the case of an accident when clearly witnessed. Otherwise, Northern Ireland is essentially the same as elsewhere in the UK.
I’ve always wondered about it when visiting the USA; see also Sweden for comparison:
It is legal to cross all roads except motorways in Sweden. Cars are required by law to give way to pedestrians (but not bicycle riders) at zebra crossings unless there is a traffic light. Pedestrians are encouraged to cross the road at zebra crossings if there is one nearby and are also discouraged from crossing at a red light. It is not illegal to jaywalk, however, and it is common to see people in cities crossing at a red light if there are no cars near. Taking risks and running across in front of cars is not usually acceptable behavior, though.
Why make such a big thing about crossing the road, that you can get arrested for it?