There�s 2 separate things here. One is the notice you should be given, both in terms of time and money if you don�t work it. Basically, for 5 year�s service I would expect your notice to be 5 weeks. That means they either have to tell you 5 weeks before your termination date that you are going to leave through reason on redundancy or they pay you the equivalent of 5 weeks pay. This may be taxed.
The second part is the redundancy payment itself, which is not taxed. This is worked out on your age and your length of service, so I can�t guess what it�s likely to be. However, you need to look on the website below for �ready reckoner� (right hand side, related links) and it�ll work it out for you. The weekly pay in this statutory amount is capped at �310, but as buildersmate says, some companies do waive the capping and do the sum based on your actual pay, but they don�t have to.
There�s lots of information on
http://www.berr.gov.uk/employment/redundancy/i ndex.html
Hope this helps.