Ignore this thread, after speaking to Microsoft again, yes you can do a bulk purchase if you combine schools, BUT, there must be some legal form of connection with the schools, such as in the same academy group, same LEA etc.
@Teejay/Plexer - You can team up with other organisations. However, you will require special permission from Microsoft to do so. The primay reason is to ensure that these memebers are qualified educational users and to ensure that the organisation is prepared to give their members the necessary information regarding the terms and conditions of their agreement. I will find out the specifics of the Consortia organizations, i.e LEA or location.
The licensing person from MS at the recent conference discussed this and said that 'multiple schools' means 'multiple schools working as one entity, not multiple random schools who decide to team up'. So, if you're a full federation, you are a single entity with multiple schools. If you're just a group of schools who happen to work together, than that wouldn't apply.
That was her definition anyway.
Further to Tony's posting ...
Schools which are considered to be a single entity are those with hard or soft federations (and having binding agreements on this, not just partnerships), members of the same academy group or with a set of shared services, schools which have reached an agreement on a buying consortium (again, having the documentation around this), schools who are purchasing via an LA or regional purchasing agreement as a group of schools ...