Ilex Hairstreak - Satyrium ilicis
The Ilex hairstreak is very similar to the false ilex hairstreak. Generally, the female has an orange flush on the upperside of the forewing, but so do some false ilexes. According to the books, you must look carefully at the marginal and submarginal markings on the underside of the hindwing. In the ilex hairstreak, especially the female, the orange spots are branded internally and externally with black. They don't mention, but they usually show in the pictures, a further internal pale edge to the black. In addition, the marginal white line is generally more or less complete. All these features are visible in these pictures, taken a year apart in the same place.