We don't have a lot of shore angling, so maybe there just isn't the demand? I'm a casual angler that's mostly just enjoying some fresh air, so not noticed the lack of bait. You can buy online, Friends down South have used yorkshire-worms.co.uk for compost worms, I have not checked but if they use Royal Mail then might be a 2 day not 2 week "next day" delivery.
Edit: Translated into English!