You only require 10 for this achievement but there are at least 15 to collect.These are all located in one area called: Wyndham VillageTo reach the village, from the start of the game you will come out into Slattendale, head north towards the purple aura coming from the power plant in the distance and keep following the stream north to avoid enemies. At the end of the stream you will see a sewer entrance of some sort and to the right of that some British flags next to an exit, if you use that exit it will take you into Wyndham Village where you can start your gnome hunt.
At Wyndham VillageYou can do these in any order but for me I start at the inn:
Grendels Head, then work clockwise around the map. Follow along from 1 to get them all but if you're after specific gnomes I have added the coords for each.
- On the floor outside Grendels Head, directly opposite the front door (34.2E, 79.4N)
- Head west from Grendels Head to the Village Hall, as you face the front door to the right side is a barrow with the gnome sitting next to it on the floor (33.4E, 79.2N)
- Continue west from the Village Hall and up to the Church, literally just above the Village Hall. Head inside the church and there will be a small staircase on the left side of the Church leading up to the roof top, go up and the gnome will be sitting on the wall in front of you (33.1E, 78.7N). Beware bats will attack you here if you wait too long.
- From the Church go down the steps and continue west, follow the main path along and through the small checkpoint with 2 soldiers. After the truck on the left will be a small house, at the front door of the house that's chained up will be the gnome sitting on the right side wall/frame (30.5E, 78.9N).
- From the house head back down the path east passed the 2 soldiers at the checkpoint, from this point head directly north cutting across the land following your compass. You will drop down and go over the stream and you will see the red telephone box. If you face the telephone box, on the left is a building and at the side of it is your gnome sitting on the sofa outside, you should be able to see it from the telephone box (31.2E, 82.4N).
- From the sofa head down the main path south east and over the small bridge, half way down will be a small open building like a stone bus shelter and inside will be a gnome on the floor (32.4E, 81.8N).
- From the shelter continue down the same path southeast, go through the gates that are open and as you pass through the gates you will see the white house on your right side, just behind the white house between the houses is a passage way, follow it through and you will find the gnome sitting on a window sill (33.9E 81.1N).
- From the house head east following the path and when you get to bridge street continue east following the left path way. At the end of the path you will see a building ahead of you with a flag on and a beck street sign, to the right of the building is a gap leading to the rear of the house, go through the gap and head right then climb over the stone wall. After going over the stone wall there will be a chained up door saying keep out, directly opposite that at the corner of the building will be the gnome sitting on the floor (35.8E, 81.8N)
- Now go through to the front of the houses again back on to beck street and this time follow the path south, you will come to the small bridge going across the stream and sitting next to the bridge on the right side of it will be the gnome, you will need to cross the bridge to get it (35.5E, 80.6N).
- From the small bridge do not continue on beck street and instead go through the gates on the right side on to fern bank, this should be west. Follow the path until you reach the small wooden outpost with the soldier standing there, opposite that on the left side is an entrance to the little tea room, go through and then through the archway and you will find the gnome sitting on the window sill under the little tea room sign (34.6E, 80.4N).
- Now from the little tea room go back the way you came and this time back on to beck street heading south, go through the gate and just passed the wooden outpost on the right is a small park/play area and a couple of buildings, between the two buildings you will find a gnome on the floor tucked in next to the plant pot and steps (35.1E, 79.6N).
- From here continue south along the path to reach mill lane, head east along mill lane and open the gates at the outpost, continue on and just after the bus stop follow the path left/north into the mill grounds. You will find the small bunker/shelter in the centre of the grass and sitting in front of it will be the gnome (36.4E, 79.6N).
- From the small shelter face east and behind the buildings in front of you will be the gnome next to a smaller building sitting on a bench, use the side passage on the left to get behind the building then go through and you'll see it on your right side (36.8E, 79.6N).
- Now go to the front of the building and head south along the path, at the end of the path you will see steps directly in front of you heading up again south and between the houses, go up the steps and follow it through to the rear and you will find the gnome sitting on the picknick table at the back next to the tree and stream on the south side (36.4E, 78.1N).
- From the picnic table go back to the steps north and onto the pathway. This time head west and exit the area, once you're passed the gate head south onto ridgeway and follow it along until you reach the outpost with several guards and the exit to the area, do not exit the area and instead look directly south/southwest and you will see further up a building with a closed red barn door or at least slightly ajar, go up to the barn door and on the right side climb the gate then climb the stone wall to get behind it and find the gnome on the floor inside next to the wicker basket (35.5E, 77.5N).
If you need more help with this you can follow my video guide below which will direct you to all gnomes: