Hey Glyn,
-Add Theory of Poker (Sklansky) to the shopping list,
-Check out the sticky posts in basically every subforum that's poker-related, even if you never play NL, Razz or Full Ring, if it's stickied it'll help your game. You'll find a few weeks worth of reading there; start with Pokey and Fimbulwinter's posts. I found this forum when I just started out, and thanks to these 2 guys alone I was able to turn my lousy 50 USD first deposit into 1K.
-If you want a break from reading then stuff like
MTT Live PXF Directory is huge.
Hope this helped you a bit, and gl at the tables.