Oh, I wish I had read these reviews before using this awful company.
I would not advise using this company to book flights, unless you are using a Mastercard debit card. You will be charged at least an extra 7% without, as far as I could see, any due warning. I was really surprised when I realised that I had paid much more than I was expecting to pay, so I wrote to Opodo immediately. I finally received a reply, saying, "When you reach the payment stage, if you enter a card different to a Mastercard Debit, then the price will change to the new price for the service charge, plus any credit card fees (charged at 2.5%). This is still before you commit to 'Buy It Now'. As we have offered the opportunity to view the pricing before you select your flight and again before the flight has been confirmed for purchase, on this occasion, we are unable to offer you a refund of these charges.
I do not find this acceptable. So, if you do choose to use Opodo, just beware of this before you do.