Jumping Plant Lice (Psylloidea)
Although it's quite old, the main reference I use for these is the RES key to Psylloidea by Hodkinson & White. There's also an RES handbook covering nymphal stages, also by White & Hodkinson. The British Bugs website also has some really good information and photos of many species.
It can be quite difficult to get a good look at the shape of the genal cones on a specimen but this can become easier if you clear the specimen in potassium hydroxide solution first. Sometimes the male parameres are easier to see on a cleared specimen than a dried one and the same applies to the female terminalia - especially, as I have discovered recently, if you need to measure the proctiger as the key demands for some species. I generally get as far as I can with keying it before clearing though, as the process removes other characters such as colour.
Family Aphalaridae
Aphalara polygoni
Family Psyllidae
Broom Psyllid Arytaina genistae
Arytainilla spartiophila
Baeopelma foersteri
Cacopsylla ambigua
Cacopsylla brunneipennis
Cacopsylla melanoneura
Cacopsylla peregrina
Cacopsylla rhamnicola
Chamaepsylla hartigi
Psylla alni
Psyllopsis fraxinicola
Family Triozidae
Trioza galii
Trioza remota
Trioza centranthi
Trioza urticae