Hi Kido, welcome to the forum.
I'm sure you'll get plenty of other feedback from others in the next few days, but having spent 7 years working with categorised vehicles I found that most dealers stayed well clear of them.
Categorised cars generally fetch around 50% of their non write off value at auction, the big franchised and independents won't touch them, so your pool of bidders is limited.
You are always going to be fighting an uphill battle, as the industry has always been very much against written off cars. The biggest problem is the patchy quality of repairs and the charlatans out there, I have sadly seen too many that are dangerously rebuilt in a back street garage on the cheap, no one wants to risk being associated with that.
Have you considered getting these officially checked. Although this would not remove them from HPI's condition alert register, it does mark them as "Condition Inspected", which is a check of the quality of repair and safety ( unlike a VIC test which is purely identity). This may add value and make the cars more attractive