If you build up the fertility of your veg patch with compost and organic material the worms will automatically move in. A good compost heap will also attract worms if it doesn't get too hot or acidic.

Yea, I was gonna say, just put some decent composted manure or garden compost, organic soil conditioning compost, anything like that on it. The worms move in as soon as the conditions are right, and are often present in the composts anyway, even if you can't see them.

In 2009 we took over part of a neighbours garden for vegetables. When we first dug it over I found just two worms and was worried. After working the soil it is now alive with worms. Just keep working some humus into it and avoid relying on chemical fertilisers and it will be OK on its own.
Of course, if you really want to buy worms - how does £1 apiece into Bulbaholics pension pot sound ;-))))

thanks 2 all