just keep deep digging say in January and get every bit of white root out of the soil, keep pulling at the slightest trace of bindweed whenever you see it, avoid weed killers etc as harmful to wildlife. I never totally eradicate but it can be kept to a minimum.
solomon's seal is a fascinating plant but that and hostias will be preyed upon by slugs and snails. Use nemotodes for slugs, collect snails and relocate regularly.
lovage (in light shade)
I've taken seeds from last year's foxgloves and they've grown to plants in pots which I'll put out in March but the original plants haven't kept going. I think I'm going to have to do this every year.
What about honeysuckle,they are easy to grow,smell beautiful and have red berries for the birds. Sorry, I forgot you are going to grow it in a pot,I don't think that would work for honeysuckle.
Check out what the Organic Gardening Catalogue has because they offer a variety of different things to feed soil and make it more managable .Our soil is pretty heavy but regular manure really helps.Do you grow comfrey?That is a very good green manure.
apart from broccoli and chicory are there any other veg that slugs don't like? Is there any veg than snails won't eat?