Liz and PRINTMISS - thanks for taking the moderate route (root again, sorry).
Most, if not all, of the plants on my balcony don't last beyond around 3 years and I can go with that, but there's a danger these beasties are taking over.
Its interesting though to note what they DO NOT attack alongside plants that they have munched up.
I have an antirrhinum (spell check?) plant which is still laughing, although it has just stopped blooming, in a pot where two other plants have succumbed.
Also I have a sturdy marjoram plant, in a pot where an accompanying wallflower plant and a lettuce wilted, then died. I spotted a sneaky vile fat white weevil caterpillar at least once under their wilted remains.
(Wikipedia says vine weevil damage is done by the caterpillars in Autumn-Spring - from eggs laid by the aforementioned sweet black mini-beetles).
,
So, Liz and PRINTMISS, since I need to replace compost (ideally, organic stuff but not always practical) every 2 or 3 years at least, well, maybe that's not a bad option after all.
to you all, its lovely to give bouquets especially to fellow gardeners 
Or, VQ, if all else failed, I am up for the nuclear option.