Hi Neil,
You may still be able to upgrade if you follow the steps below:
Log in/register on Promethean Planet, click on Support>Download ActivInspire>Choose your Language>Download>click on "I have an ActivExpression, ActiVote, ActivBoard (excluding 100, 300 & 500) " and follow the instructions.
Please let us know how you get on with this.
Thanks,
Miguel Silva
Promethean Technical Support