Gth, how much of the detail do you know?
It sounds like a fairly lengthy investigation by the Special Compliance Office, and if they really have said nothing since, then it is only because that they think the fraud is ongoing.
They do randomly prosecute in the event of fraud, in order to "make an example". So without wishing to worry you further, if they're going down this route, then they are looking for a heavy penalty - your dh's solicitor should have warned you about this. Are you sure that dh is giving you the full picture?
When you had suffered the dawn raid, did your solicitor not do anything then? If not before, that would have been the time to meet with the IR and discuss everything. The IR would have already have been to the court at that stage in order to get authorisation for the raid.
Is it actually your dh being prosecuted or is he just being dragged in as a witness.
I'm sorry that you're going through this. In some ways the case is just random - the IR will carry out a numbe of prosecutions (and publicise them heaviliy) just to make a point. I've been invloved in similar cases and it is not pleasant.