"Do you know it they're available in silver alloy colour too? 
"
I think they were avaliable in silver, iirc. I'll try and find out who they came from later, but i just did a search on ebay for white wheel nut covers, only cost a couple of quid for 20
.
Personally I didn't like the 'standard' black nuts 'cos they looked a bit dirty so took a punt on the covers just because they were cheap. Obviously not everyones cup of tea, but they look okay for now.
Cheers,
Rich