Mulching with freshly fallen leaves.

[Two_Sheds]

I imagine a sprinkling of salt (seasoning) would do them in too

[jacob]

If you are finding flatworm,the chances are you will still have some earthworms and when the earthworms are all gone the flatworm population will diminish also. To reduce the flatworm population put a shovelful of soil in a carrier bag and set it down on the ground. Check regularly under the bag and pick off any flatworm. Prof Boag of Dundee University recommends immersing them in boiling water to kill them. I have found that neat J***S fluid kills them immediately.

Cheers -- this is what I do and they seem to only be around the compost heap, not in the main plot (excepting the one I found alarmingly tangled round a carrot a couple of years ago; no carrots this year, but that's another story).

I'm usually very reluctant to squish anything, however in this case I make an exception. I find that rubbing them into nothingness undershoe on the concrete does the trick.

[Two_Sheds]

they seem to only be around the compost heap

They're definitely flatworms then, not sloe worms? *worried*

[jacob]

They're definitely flatworms then, not sloe worms? *worried*

One of these horrid slimy worm-like thing:
New Zealand flatworms - Problems: Lawns - gardenersworld.com

Definitely not a slowworm, you couldn't mistake the two. And I reckon it's too cold for them (slowworms) up here!

My guess is that the flatworms have sneaked in with something from the garden centre and like the worms in the compost heap.