Based on a survey sample of 1012 businesses in UK, 69% have said that their invoicing systems are not integrated with their own accounting systems. Among those who have integrated, only 10% achieved seamless data exchange between their own systems. It seems that the survey has not collected data on exchange of invoices electronically between organisations (suppliers and buyers). One can assume this might be close to 0%. 
Another figure from the report shows 14% of the businesses using e-invoicing at present, with another 9% planning to implement such solutions within the next 2 years. Once again there is no reference to use of many-to-many Value Added Networks (VANs) such as ebdex Document Exchange for document exchange seamlessly between suppliers and purchasers. Reference: IT in Business – a review of the market for financial and business software – Research Report Apr 2006 (ICAEW Survey 2006)