//it wasn't registered, as required under Data Protection Act.//
That could make the tribunal hearing quite interesting.. :-)
However, if the misconduct - you didn't go into detail - is of a type which the tribunal is unlikely to condone then maybe the dismissal could be upheld.
"But all the other cars in the outside lane were also doing 80" is not a valid defence against a speeding ticket.
It's strange that many whisleblowers have an Achilles' heel which leaves onlookers thinking "oh, they only blew the whistle 'cos they got caught misbehaving", like blowing the gaffe is their way of firing back as they go down in flames. On the other hand, maybe the truth is everyone has misbehaved at some stage but it is tolerated, so long as they keep mum about the 'big bad' which the employer has perpetrated.