What is eating the roots of these plants?

[Suncottage]

I have one particular flowerbed that in the last week has 'killed' three plants including a very long established white heather.

They were turning brown and I could literally just lift them out of the ground as the roots had gone?

What has happened?

you have vine weevil.... in adult form the just eat leaves, in grub like form they eat the roots of the plant. i lost alot from it this year and my dad (trained horticulturalist) said really the only thing to do is get rid of the soil.... now mine were in pots so im not sure how practical it would be for you to replace the soil of a whole bed but they will just eat everything.
this may help you www.garden.ie/gardeningtroubles.aspx?id=651
good luck

There is another possibility - Harrod Horticultural offer a nemotode which is a vine weevil muncher. Here's a link:

www.harrodhorticultural.com/HarrodSite/category/Vine_Weevil/

I dont work for them by the way but I knew they have a good pest control section.

There is also an insectice called Provado that kills them - but it is pretty hardcore and nematodes are a nicer option!

LoveInAColdClimate - not a great range of options for the vine weevil - poisoned or eaten alive by a nematode!

No, true - pretty much sucks to be a vine weevil, eh?! I used some Provado earlier this year as my neighbour had a major infestation and I didn't want to wait for the nematodes to be delivered in case it spread further - the instructions were pretty terrifying! We're TTC and I spent the next week worrying that I had caused some terrible birth defects (but then AF arrived!).