A chiv is very closely related to a pikey
and indeed is all pikey, a subset of pikey, if you will.
The main difference is that a chiv's favourite style of casual-wear is Burberry.
Burberry baseball caps are a favourite amongst chivs but you do see Burberry shirts, shorts, shoes etc and very rarely you may spot a truly hardcore chiv bedecked head-to-toe in Burberry....nnnnnice.
A secondary difference is that a chiv is generally more stupid and therefore more vicious than a pikey...watch out...doubly nnnnice.
Check out that chiv fool on the other side of the street in his Burberry pyjamas.
There were a bunch of proper chivs hanging by that BMW...doubt it's there anymore.