Unless your contract said that you were entitled to a tracker, then you were not entitled to a tracker.
EBS was very reluctant to offer trackers and so I would be surprised if their teaser deals which were designed to attract new business gave a right to a tracker.
The historical rate has nothing to do with it. Check your contract when you took out the mortgage. If it said you were entitled to a tracker, then you should ask why you were not offered one and you have a case. If it says nothing about trackers, you are not entitled to one.