New radio

Hi,
I am looking to replace the radio in my golf with something that I can connect my iphone too, either by USB or Bluetooth. I have seen that Kenwood do a sat nav/bluetooth unit for the VW but second hand on eBay these items sell for £350-£500.
Is there a cheaper alternative? I have noticed on eBay there is a new one by Xtrons that looks like it will fit. Does anyone have one of these? Are they worth the £140 or are they no good? I don't really want a single din, but one that fits exactly.
Thanks