Sounds to me that they were forced to close and are trying to make amends. I think you've had a bit of a result as I have never heard of this happening before and they must have been happy with you or they could easily have got someone else, I feel it is unlikely they would do this to you again.
I have lost thousands over the years with companies going bust or just closing, and in my experience you never see the money again. As to the Government writing off bad debts, just can't see it happening, I will speak to my accountant later and see what he says.
I think they have swallowed more pride than you by asking you back. Glad to hear you can get back on your feet again, best of luck, if any work comes up I can't handle I'll give you a shout, do have a school coming up near you soon.