Lucky you, means the soil's fertile. You're getting them now because the ground is wet - autumn and spring are the times when worm casts become really noticeable. In summer its too dry, in winter its too cold. I know it can be unsightly, but look at this way - each little pile of worm cast is highly nutritious and feeds the grass and improves the soil, and every hole they make to deposit a worm cast aerates your lawn. When they're dry, you can brush them gently over the grass - if you have large deposits and they're wet, scoop them up with a trowel and place on your borders.

I understand your woes John.

My front and back gardens are so overrun with them that it looks shocking out there :-(

I see them in a slightly different light now Bamboo :-/

Give thanks that you have worms!

Here's a point of interest. In an acre of good ground, earthworms are estimated to move about 18 tons of soil each year, aerated and enriched, and to spread that on the surface of the ground. An (almost) automatic mulch. Help them out, use fewer chemicals, and let them do some work for us. Phil J

Thank you to all who have responded to my question.
It's good to know that worms and their casts are doing good things to my lawn. Pity they can't kill the weeds too!