Snails love Clematis and I find they climb up. You could try picking them off, yeast traps, beer traps, place an upside down pot where they will gather, copper bands are also good for around pots. Keep the area open and dry and avoid places where they can stay cool such as under wood or crocks. Encourage other wild life in your garden such as frogs and Hedgehogs as they will keep the numbers down.

You must be a bit damp with lots of snails. I would like some water to drop from the heavens here in Essex and snails would be welcome. The snails can be picked up and disposed of nicely by placing somewhere else, or more nastily.....whatever you want to do. They are part of nature. A slug ate a major new shoot off my clematis....I do get nasty with them but they have their place too.

That maybe Dorjac! but in my garden they do more harm than good so I encourage frogs, hedgehogs and other wildlife to help me control the pests.

Pieces of wood or rolled-up newspaper can be used to trap snails and slugs. Put them down in the evening, grab your trowel in the morning, and scoop up and bin all the ones that took advantage of the new shelter. After a few nights of this, the population will be reduced, and damage will drop dramatically.

we are not concerned with damage to plants but want a permanant solution to the destruction of the breeding ground

So, the mere existence of the snails bothers you? Or are they causing other problems?