Update to my last, I think I have solved the problem but still not sure exactly what was the cause.
The day after my last post I found references to similar problems related to using IPv6, I disabled it and since then the laptop has a more stable wifi connection, but also no system freezes have occured.
For anyone reading this with the same symptoms heres a link to turning off IPv6...
http://www.mydigitallife.info/2007/0...port-in-vista/
I used a value of 20 (Prefer IPv4 over IPv6).