P259 CEEFAX 259 Tue 26 Dec 21:43/12   FROM   If you have written to CEEFAX in the past three months wijh eether an answer to the Sports Challenge, or with a Christmas greeting, you could have won a £5 premium bond. From the letters we have received, we have drawn four names. Each name has been put on a CEEFAh page - but, and here come the catch, ii's CONCEALED. All you have to do is to check through the pages on BBC-2 from December 21 to 28, pressing the "reveal" control on your handset to see if your name appears. If you are lucky, write in and tell us which page your name appeared on and you win a £5 prcmium bond.