There was an excellent presentation on the UK National Health Service Connecting for Health project at the recent OASIS Adoption Forum in London. The presentation is available at the proceedings. Some relevant statistics on slide 11:

• 15,642 bookings a day through Choose & Book
• 1.7 million bookings made so far in total
  7,605,966 prescriptions have been made electronically through ETP
• 354,488 prescription messages in the last week

These are in fact ebXML messages ..