One useful tip - don't read a post by spaw whilst eating a peanut butter sandwich and drinking a glass of water. Especially don't do it if you're at work and there's ppl ready to laugh at the results, as half goes down your lungs, a third goes up your nose, and the remainder comes out of your eyes, whilst you desperately try to keep your mouth closed to avoid coating the keyboard and monitor. Crunchy peanut butter too...
Airto, try nailing a strip of sandpaper around the flap. Slugs and snails don't like crawling over that.
A guy I met out walking once swore that the best insect repellent is to dab a drop of vinegar on your neck. Downside is that it keeps everyone else away too, cos you'll smell like a chip-shop.