It's actually the severity of the case that counts. If it's Bernie Madoff level of fraud & concealment or serial murders which would be tried in the Crown Court, then there's no statute of limitations.
If it's a magistrates job, then the limitation is 6 months. If it's to do with debt, contracts etc, then it's 6 years.
Having looked deeply into this, I've no idea where the PL are going with this, especially from a statute of limitation angle.
If what we're accused of is that serious, they're legally bound to call in the law. The fact they haven't speaks volumes.