Hi Ronan,
Technically the Pass Certificate for Life in the UK has indefinite validity. The result is also sent electronically to the Home Office after you pass the test. And in a politically correct language, Home Office says that they do not keep these electronic results indefinately, they don't say how long they do keep the results 🙂.
I don't think if you pass your exam before the exam changes in April 2007 you will be at any loss. Just to be sure, you can call up Home Office.
All the best with your exam.
Cheers
Navneet