Your suggestions are superb. I can now enthusiastically affirm that Membership of FlyerTalk has been of direct and undeniable benefit to me. I have now tried using Chrome, and have competed the purchase just fine. Thank you for your suggestions. This whole sorry episode is a great illustration of my inability to think outside the box. I must agree that perhaps the BA website, or Kimberley of their Customer Service team, might have suggested "try a different browser if your first attempt does not succeed". I am now a wiser man, slightly shamefaced, and looking forward to having a drinks at BA's expense.