There is confusion over the rules entering France from the UK. On 11 March, the French government announced it was easing restrictions on travel from the UK. From 12 March, arrivals no longer need to justify an essential reason to enter France. HOWEVER, as the UK government website states (see below), foreign travel is still illegal so despite France easing restrictions, it doesn't help anyone in the UK! The projected date when this is expected to change and permit you to travel is May 17th 2021.
Under current UK COVID-19 restrictions, you must stay at home (or in Wales, stay local). It is illegal to travel abroad for holidays.