An english prep is very different to an american 'prep'. In england the word 'prep' isn't used, there's no real catagory, but you can easily spot them.
Girls wear the likes of Pashminas&Scarfs, All saints belts, UGG boots, Benefit, too faced etc makeup. They shop at designer stores such as All saints, Harvey nichols, Harrods, Selfridges &co etc. They also go to non-designer stores such as TopShop, H&M, Zara, Miss Selfridges.
Guys wear white trainers, poped ralph lauren and lacoste polos, scarves, baggy expensive faded jeans, tanned, extreemly handsome hair, sometimes in mohikan thingies, or over face, or just wow.
They Attend private schools, have rich familys, flashy cars, and Dolly-bird mothers.
An English prep doesnt stick to one trend, it follows the latest fashions.