Farewell

[Leanne]

Walk with me to a bank beside -- This is a good opening line, but I wonder if you'd consider an "O" address to begin? Just to plunge the reader in a little faster to the meter.
A river rippling running slow, -- I would tend to break up the "ing" endings for sonics alone, and use "a rippling river", only that phrase is slightly more cliched -- the problem (and it's a little one) with "rippling running" is that with the alliteration and the similar endings it seems slightly too "trying to be poetic"
Where wild and wary wood-things hide, -- the alliteration is beautiful in this line
In trees and roots and holes below.

Walk with me there, yet do not stay;
Begone before the setting sun
Farewells for me the split of day
And the dusk and night and the peace, -- this feels to me as if it needs a two-syllable modifier before "peace", along the lines of "silent" (though not that, obviously, just with similar meter) -- "and the" is a hurried phrase that speeds up the line and I feel it needs something to build the crescendo to lead into the soft following line
the peace so wearily won.

Walk once again to my abode,
Wander wide and wander whither
Piers poppy-pastures ploughed; -- you could try "Piers in poppy-pastures" to break up that heavy alliteration just slightly and to aid meter
Find my lych, and bring it thither;
lay it there,
and leave:
my child. -- beautiful, sad and surprising ending -- this puts a different spin on the peace and made me re-read the poem, so I picked up an entirely different set of connotations, which is what a poem ought to do

Lovely stuff, Edward.