That's a bummer Kevin.
Any way you can 'un-resign'? Was your resignation acknowledged and accepted by the employer?
If not, looks like you were very unlucky. Can't see why you would be entitled to redundancy if you resigned first.
It used to be a fairly common tactic for management to unsettle staff with fear uncertainty and doubt so that many would leave before redundancies were offered. Of course the drawback to this approach was that the company lost many of its best employees first as they knew they could get jobs easily elsewhere.
All the best.