Length: 5.5 to 7 mm. A large species with numerous white cross-veins and black mottling on the forewings, and several dark dots (not lines) on the vertex 

A. modestus has distinct dark lines on the vertex

This species can be identified from good quality photographs; these must show the vertex 

Deciduous and mixed woodlands, especially with oak. The adults can be found on various deciduous woody plants.

Adult: June to October

The nymphs probably feed on grasses.

Common. (ref.: UK Auchenorrhyncha checklist 2021 on British Bugs website)

Fairly frequent

https://www.britishbugs.org.uk/homoptera/Cicadellidae/Allygus_mixtus.html