The Oxford OATMedia Aviation Meteorology DVD is fantastic: The ATPL version (although on the face of it too much for PPL) gives a sound understanding of the entire subject, and is great for 'reading round' the subject as well as a future reference volume.
It doesn't take too much skill to determine what's not needed for PPL (Hurricane formation in the Caribbean f'rinstance) but it'll be there and ready for when you do your CPL/ATPL. Thoroughly good buy IMHO, nicely divided up into easily digestible sections with their own test questions and explanations if you get the answer wrong and excellent graphics.
I personally think you can never have too much Met knowledge...........
If this seems too much, they do a PPL DVD but as I haven't seen it I can't vouch for its quality, tho' I should imagine it's equally good.
Cusco