I too failed MET first time round. I've now finished all my exams except MET! it is definately the most difficult of the bunch. I really enjoyed the NAV exam!
I have both the Trevor Thoms books and the Oxford DVD's. To be honest I much preferred the books. I found the CD's used to send me to sleep so I didn't really learn very well from them. The books however were interesting. I always carried whatever subject I was studying at the time (I study for one exam at a time only!) with me wherever I went and would read a page or two whenever I could. At break times, lunch times, on the bus/train wherever.
I agree with the others that the most important revision aid for me was the Confuser! I got my copy off eBay. I found it was the only aid that's questions were worded close enough to the real exams to really get you thinking like a pilot as the questions are aimed at pilots not meteorologists for example.
Good Luck! You will get there but it requires discipline and determination!