I am afraid you have been the victim of a terrible scam - the whole story was fabricated, and there was nothing wrong with your PC. Worse still - they presumably now have your credit card number, so I would call your bank/card company and cancel the card. If you tell them the problem you might also get your £139 back.
This fraudster may also now have permanent access to your PC - so I would be inclined to restore to factory settings. Others may advise as to the necessity for this.
I'm truly sorry to hear this story, and am appalled at the callousness of the caller - sadly this is all too common.