I’ve planted a row of French marigolds alongside the tomatoes in the tunnel, and they are proving to be a good line of defence for the precious veg as the slugs are eating them first.
If you are revolted by slugs a beer trap might not be such a good idea unless you can get someone else to empty it! I’ve found them very effective though. Also, I had a bit of success using sheep fleece around individual plants, but it didn’t do so well in the wet summer of 2013.
Do you have any hedgehogs in your garden? It’d be worth encouraging them, they do a great job on snails.