The best place to buy Danisco starter culture is from Orchard Valley.
I like the guys at Orchard Valley as they are extremely friendly, approachable but above all, knowledgeable. Their customer service is also good and deliveries are prompt. Ask for Trevor, he is an absolute star and has helped me enormously.
Their website is: http://www.orchard-dairy.co.uk/ and they can be contacted on: 01584 811137.