Just out of interest @ScottW my Debit Card is one where the transaction needs to be authorised online at time of payment.
As some contactless terminals i.e. TfL complete their authorisations 'offline' would that impact on functionality at all?
The type of card you have shouldn't have any impact on contactless payments as they can take a maximum of 7 days to show on your account. It will, however, affect your available balance when the retailer make us aware that they're taking funds for the contactless transaction. At any point over the 7 days the funds can be deducted from your available balance, which is totally up to the retailer. I hope this helps!