The Government has announced that workers can carry forward up to four weeks of annual leave into the next two leave years. Note that this is four weeks (the entitlement under EU law) not the full 5.6 weeks under UK law.
The remaining 1.6 weeks will not be affected, although this can still be carried forward for one year but by agreement between the parties.
This is where it is not reasonably practicable for all or some of the leave to be taken in the current leave year due to the coronavirus.