Nice rule of thumb there BackPacker!
The Met exam isn't too bad actually, I seem to remember a question where you are given the F215 and on it is marked a route from say A to B and you are asked, judging from the forecast conditions shown on the F215 if it will be OK to fly or not. As long as you've studied you'll be OK!
P.S. If you haven't already done so sign up for the online Met Office Aviation briefing service... it's totally free and it lets you get used to AIRMETs, TAFs & METARs F214 &F215 etc. I found it a great help for doing my Met exam. Also comes in handy for when you come round to doing the planning for your Nav exercises!
Good luck with the exam.
Smithy