Thanks, I followed the instructions on that link and the Support Info page says
Blackberry Professional Software for Microsoft Exchange
Use the following information blah blah
Publisher: Research in Motion
Version : 4.1.4 (bundle 143)
And I think I can see where my confusion comes from, in the licence manager it says I have Small Business licences, but they must be from when we had small business for Lotus Notes. We upgraded last year to Exchange and changed BES at that point.
So it looks like we have Blackberry Professional which should have a 30 user limit. Phew, thats better.