I can find NOTHING on the CAA website..
Try the AIS website its all in an AIC:
http://www.nats-uk.ead-it.com/aip/cu...8_W_030_en.pdf There is a further well hidden doccument here:
http://www.caa.co.uk/docs/175/AN%20A...%2000%2000.pdf If you hold a valid PPL you should be OK. Put simply, you will need a valid C of T C of E or C of R for each Class on the NPPL, no more rolling validity.