If you received a "Payment Declined" email, this means the payment was not taken successfully. This means that a booking confirmation email would not have been sent.
Please note that any taken payment for this booking attempt should only be shown as pending on your bank statement if anything has been deducted from your available balance.
Your card insurer should automatically recognise that the payment was not taken so there is no outgoing to be expected - it will rectify itself automatically shortly and will return the payment to your available balance - please allow up to 5 working days.