For me, Santander will sometimes reject/hold a large payment if it is outside of normal spending and then give me a call on my mobile just to verify it wasn't fraudulent. This might require me to re-present the payment and they will watch it go through. That said, I paid over £35k for my KonaN using a debit card and had no problem, same went for my recent watch purchases which were both well over £10k and neither solicited any response from Santander. Tried buying a £90 wheelbarrow online the other week and they blocked my card! Go figure ...