Visitor visa question (London)

Hi..

I am a Canadian currently on a 6 month visitor visa in the UK.. My question is, once I return back to Canada after the 6 months, is there a rule or law that states how long before I can re enter the UK, or can I return back say after a couple of weeks and stay another 6 months..

I have checked UKBA's website and contacted the Canadian embassy plus lots of research online, but not able to find a clear definite answer..
Thanks
Helen