It cracks me up hearing of SEP's such as 172's PA28's etc doing a +180 GS.
Actually I got it wrong the fastest is actually 264kts. Below is the extract from my Garmin GPS Flitebook. Feel free to PM me for the original file. I think if you check the weather for that day you will know where the GS came from. So don't be such a smart arse.
5/03/06 C172 XP G-DAVD EGTC EGBK 1 0.1 0.1 0.1 0.1 17:19 17:27 CRANFIELD SYWELL N52 04.686 W0 36.606 N52 17.326 W0 37.615 18.2 nm 264 kt 2784 ft