Just out of pure curiosity does your delivery carrier deliver on Sundays (UK)?

We use Royal Mail, so it’s unlikely. You should have received tracking information after your item was shipped.

Royal Mail has launched a trial scheme with the opening of 100 of its busiest delivery offices UK-wide on Sundays. The company will also begin to offer Sunday parcel deliveries but this will be in the London area only.

Amazon may have put some pressure on them here.