I would use a strimmer rather than spraying. Though you would need to be careful not to bark the trees.

I would dig/pull them up if possible - the more roots you get out the less will grow again.

Strimming will not kill nettles or bindweed.

The organic method is digging it up ensuring all roots are removed.

Roundup (Glyphosate) will kill nettles and bindweed although you may need two or more applications.

Roundup won't damage the trunks of beech trees but be sure to keep it off the leaves.