Does this ship in one basic form and you can then choose whichever colour you want? It is not clear from all the reviews but it sounds like you get a few different backs that just clip on. The reason I ask is it is currently £169.99 from carphonewarehouse but is showing as available in silver only and I would prefer black. Could it be that in this case the front is silver and you can add a different coloured back? Any help would be appreciated. Thanks