Redrow, you can apply through the social insurance fund but you need to send the following:
1. Copy of audited accounts of the company for last full year of trading
2. Signed letter from accountant or solicitor that the company is unable to pay your redundancy but recognises that they have a liability to the SIF
These two items are key to getting your redundancy payment but be prepared for a long wait. I was waiting Nov 2010-Jun 2011 for the paperwork from my employer and an additional 7 months for the payment to actually come through from the social insurance fund.
If your employer is not playing ball you will have to go to the employment appeals tribunal, you have up to 12 months from your redundancy to go this route - however if it rules in your favour, you will still need the above paperwork so best to try to do this first.