How much is enough?

Would you rather win a guaranteed £100,000,
 or have a fifty fifty chance of winning
a million pounds on the spin of a coin?
This week's dilemma is a test of greed, and offers a choice between taking a gamble, or playing it safe.  Here's the scenario...

You're waiting for the bus one day when an eccentric billionaire approaches you and offers you £100,000.  He opens his briefcase containing the cash, so you can see the offer is genuine.

However, he then offers you a gamble...  You can either take the £100,000 there and then, and the money will be yours to keep, or you can risk it all on the spin of a coin for the chance of even more cash.  If you guess heads or tails correctly, the eccentric billionaire will instead give you a million pounds!  However, if you guess wrong then you lose everything and walk away with nothing.  Not even your bus fare home!

So that's the dilemma.  What would you do?  Would you take the £100,000, or would you risk it all on the spin of a coin for the chance of a million pounds?