Because other people seem happy to pay 10% over the MTGOX price?!

yeah some of those sellers have 100% markups!!!!

average is 10% markup - how do they get away with it!!!

At the moment, I have an online wallet at blockchain.
Is it safer for me to use a wallet on my own computer?
If so, what is the best way to do that and how do I go about backingit up?

Doesn't leaving a computer on 24/7 cost more in electricity than the amount of coins gained?

I can't find anywhere to buy BTC in £ sterling.
Blockchain seems to have turned off UK deposits.
MT GOX has to be sent to Japan so that costs too much extra.
Any currency conversion adds 5-6% plus bank fees!!!!!