did you tell Defence medical taht the crash was a third party fault?
if you did, it should already be a legal matter as Defence medical (or department of Finance) will likely lodge a 3rd party claim on your behalf.
You could "innocently" mention this as the "guilty party's" failure to cooperate could render it very expensive for them to renew the insurance, and more so if they don't own the vehicle involved
it could be the vehicle was where it shouldn't ahve been!
also, follow up with RTA about how you get address of other party so you can start civil preceedings