The mother book of all is the "BRB" - alias the big red book, or BS7671. Have seen them for about ÂŁ45 quid, however general pric is around ÂŁ60-70. Dont get this yet mate, you need your tools first, but I would definately get from your tools budget the OSG or, on site guide. It will explain to you why you do what you do each day, and of course everything in it is based on BRB anyway. A better book in my opinion is the electricians guide to the building regs, again about ÂŁ15, it seems to be a bit clearer than the osg.
The NICEIC do three books, called snags and solutions, book three is not yet in my grubby mits but is on its way, these books are brill and tell you how to get over common problems, however, you have to know you have a problem in the first place which, these books will point out, so are an excellent learning aid, you dont need them yet though mate as you will have the finest thing of all by your side, an experienced Sparky.